ci: gate go/java/python tool caches to github-hosted runners (#12001)

Follow-up to #11985/#11986: setup-go/setup-java/setup-python steps
added or restructured since (e.g. by #11981's shared-artifact layout)
were missed. On self-hosted runners setup-go restores/saves a ~5GB
module cache archive per job — pure waste when the module cache is
already on local disk — and the restore blocks the job for minutes.

.github/workflows/rust-volume-server-tests.yml

@@ -65,6 +65,7 @@ jobs:
         uses: actions/setup-go@v7
         with:
           go-version-file: 'go.mod'
+          cache: ${{ runner.environment == 'github-hosted' }}
 
       - name: Install Rust toolchain
         uses: dtolnay/rust-toolchain@stable