Run actions/setup-go after checking out complement (#16567)

.github/workflows/tests.yml

@@ -633,11 +633,14 @@ jobs:
         uses: dtolnay/rust-toolchain@1.61.0
       - uses: Swatinem/rust-cache@v2
 
-      - uses: actions/setup-go@v4
-
       - name: Prepare Complement's Prerequisites
         run: synapse/.ci/scripts/setup_complement_prerequisites.sh
 
+      - uses: actions/setup-go@v4
+        with:
+          cache-dependency-path: complement/go.sum
+          go-version-file: complement/go.mod
+
         # use p=1 concurrency as GHA boxes are underpowered and don't like running tons of synapses at once.
       - run: |
           set -o pipefail