Drop Bionic from Debian builds (#11633)

* update Trove classifiers to remove py36

* stop building bionic

* update dh-virtualenv

* newsfragment

* fix newsfragment

* update version refs

* another try at correct tag

* Update changelog

docker/Dockerfile-dhvirtualenv

@@ -16,7 +16,7 @@ ARG distro=""
 ### Stage 0: build a dh-virtualenv
 ###
 
-# This is only really needed on bionic and focal, since other distributions we
+# This is only really needed on focal, since other distributions we
 # care about have a recent version of dh-virtualenv by default. Unfortunately,
 # it looks like focal is going to be with us for a while.
 #
@@ -36,9 +36,8 @@ RUN env DEBIAN_FRONTEND=noninteractive apt-get install \
         wget
 
 # fetch and unpack the package
-# TODO: Upgrade to 1.2.2 once bionic is dropped (1.2.2 requires debhelper 12; bionic has only 11)
 RUN mkdir /dh-virtualenv
-RUN wget -q -O /dh-virtualenv.tar.gz https://github.com/spotify/dh-virtualenv/archive/ac6e1b1.tar.gz
+RUN wget -q -O /dh-virtualenv.tar.gz https://github.com/spotify/dh-virtualenv/archive/refs/tags/1.2.2.tar.gz
 RUN tar -xv --strip-components=1 -C /dh-virtualenv -f /dh-virtualenv.tar.gz
 
 # install its build deps. We do another apt-cache-update here, because we might
@@ -86,12 +85,12 @@ RUN apt-get update -qq -o Acquire::Languages=none \
         libpq-dev \
         xmlsec1
 
-COPY --from=builder /dh-virtualenv_1.2~dev-1_all.deb /
+COPY --from=builder /dh-virtualenv_1.2.2-1_all.deb /
 
 # install dhvirtualenv. Update the apt cache again first, in case we got a
 # cached cache from docker the first time.
 RUN apt-get update -qq -o Acquire::Languages=none \
-    && apt-get install -yq /dh-virtualenv_1.2~dev-1_all.deb
+    && apt-get install -yq /dh-virtualenv_1.2.2-1_all.deb
 
 WORKDIR /synapse/source
 ENTRYPOINT ["bash","/synapse/source/docker/build_debian.sh"]