Bump base64 from 0.21.7 to 0.22.1 (#18666)

Bumps [base64](https://github.com/marshallpierce/rust-base64) from
0.21.7 to 0.22.1.
<details>
<summary>Changelog</summary>
<p><em>Sourced from <a
href="https://github.com/marshallpierce/rust-base64/blob/master/RELEASE-NOTES.md">base64's
changelog</a>.</em></p>
<blockquote>
<h1>0.22.1</h1>
<ul>
<li>Correct the symbols used for the predefined
<code>alphabet::BIN_HEX</code>.</li>
</ul>
<h1>0.22.0</h1>
<ul>
<li><code>DecodeSliceError::OutputSliceTooSmall</code> is now
conservative rather than precise. That is, the error will only occur if
the decoded output <em>cannot</em> fit, meaning that
<code>Engine::decode_slice</code> can now be used with exactly-sized
output slices. As part of this, <code>Engine::internal_decode</code> now
returns <code>DecodeSliceError</code> instead of
<code>DecodeError</code>, but that is not expected to affect any
external callers.</li>
<li><code>DecodeError::InvalidLength</code> now refers specifically to
the <em>number of valid symbols</em> being invalid (i.e. <code>len % 4
== 1</code>), rather than just the number of input bytes. This avoids
confusing scenarios when based on interpretation you could make a case
for either <code>InvalidLength</code> or <code>InvalidByte</code> being
appropriate.</li>
<li>Decoding is somewhat faster (5-10%)</li>
</ul>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="e144006974"><code>e144006</code></a>
v0.22.1</li>
<li><a
href="64cca59ddb"><code>64cca59</code></a>
Merge pull request <a
href="https://redirect.github.com/marshallpierce/rust-base64/issues/271">#271</a>
from JobanSD/patch-1</li>
<li><a
href="838355e0ac"><code>838355e</code></a>
Correct BinHex 4.0 alphabet according to specifications</li>
<li><a
href="bf15ccf30a"><code>bf15ccf</code></a>
Merge pull request <a
href="https://redirect.github.com/marshallpierce/rust-base64/issues/270">#270</a>
from marshallpierce/mp/clippy</li>
<li><a
href="fc6aabee8a"><code>fc6aabe</code></a>
Appease clippy</li>
<li><a
href="9a518a2d5d"><code>9a518a2</code></a>
Merge pull request <a
href="https://redirect.github.com/marshallpierce/rust-base64/issues/267">#267</a>
from bdura/patch-1</li>
<li><a
href="d96c80f242"><code>d96c80f</code></a>
Merge branch 'marshallpierce:master' into patch-1</li>
<li><a
href="5d70ba7576"><code>5d70ba7</code></a>
Merge pull request <a
href="https://redirect.github.com/marshallpierce/rust-base64/issues/269">#269</a>
from marshallpierce/mp/decode-precisely</li>
<li><a
href="efb6c006c7"><code>efb6c00</code></a>
Release notes</li>
<li><a
href="2b91084a31"><code>2b91084</code></a>
Add some tests to boost coverage</li>
<li>Additional commits viewable in <a
href="https://github.com/marshallpierce/rust-base64/compare/v0.21.7...v0.22.1">compare
view</a></li>
</ul>
</details>
<br />


[![Dependabot compatibility
score](https://dependabot-badges.githubapp.com/badges/compatibility_score?dependency-name=base64&package-manager=cargo&previous-version=0.21.7&new-version=0.22.1)](https://docs.github.com/en/github/managing-security-vulnerabilities/about-dependabot-security-updates#about-compatibility-scores)

Dependabot will resolve any conflicts with this PR as long as you don't
alter it yourself. You can also trigger a rebase manually by commenting
`@dependabot rebase`.

[//]: # (dependabot-automerge-start)
[//]: # (dependabot-automerge-end)

---

<details>
<summary>Dependabot commands and options</summary>
<br />

You can trigger Dependabot actions by commenting on this PR:
- `@dependabot rebase` will rebase this PR
- `@dependabot recreate` will recreate this PR, overwriting any edits
that have been made to it
- `@dependabot merge` will merge this PR after your CI passes on it
- `@dependabot squash and merge` will squash and merge this PR after
your CI passes on it
- `@dependabot cancel merge` will cancel a previously requested merge
and block automerging
- `@dependabot reopen` will reopen this PR if it is closed
- `@dependabot close` will close this PR and stop Dependabot recreating
it. You can achieve the same result by closing it manually
- `@dependabot show <dependency name> ignore conditions` will show all
of the ignore conditions of the specified dependency
- `@dependabot ignore this major version` will close this PR and stop
Dependabot creating any more for this major version (unless you reopen
the PR or upgrade to it yourself)
- `@dependabot ignore this minor version` will close this PR and stop
Dependabot creating any more for this minor version (unless you reopen
the PR or upgrade to it yourself)
- `@dependabot ignore this dependency` will close this PR and stop
Dependabot creating any more for this dependency (unless you reopen the
PR or upgrade to it yourself)


</details>

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Cargo.lock

@@ -65,12 +65,6 @@ dependencies = [
  "windows-targets",
 ]
 
-[[package]]
-name = "base64"
-version = "0.21.7"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9d297deb1925b89f2ccc13d7635fa0714f12c87adce1c75356b39ca9b7178567"
-
 [[package]]
 name = "base64"
 version = "0.22.1"
@@ -380,7 +374,7 @@ version = "0.4.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b3314d5adb5d94bcdf56771f2e50dbbc80bb4bdf88967526706205ac9eff24eb"
 dependencies = [
- "base64 0.22.1",
+ "base64",
  "bytes",
  "headers-core",
  "http",
@@ -500,7 +494,7 @@ version = "0.1.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dc2fdfdbff08affe55bb779f33b053aa1fe5dd5b54c257343c17edfa55711bdb"
 dependencies = [
- "base64 0.22.1",
+ "base64",
  "bytes",
  "futures-channel",
  "futures-core",
@@ -1190,7 +1184,7 @@ version = "0.12.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cbc931937e6ca3a06e3b6c0aa7841849b160a90351d6ab467a8b9b9959767531"
 dependencies = [
- "base64 0.22.1",
+ "base64",
  "bytes",
  "futures-core",
  "futures-util",
@@ -1464,7 +1458,7 @@ name = "synapse"
 version = "0.1.0"
 dependencies = [
  "anyhow",
- "base64 0.21.7",
+ "base64",
  "blake2",
  "bytes",
  "futures",