Stop paying the unreachable cache server's timeout

setup-go caches by default. act_runner's built-in cache server binds to
an address job containers cannot route to, so every restore and save
blocks until it times out:

  Failed to restore: getCacheEntry failed: connect ETIMEDOUT 10.0.2.12:40789
  Failed to save:    reserveCache failed: connect ETIMEDOUT 10.0.2.12:40789

That was 634s of a 946s build. Disable caching until the runner's
cache.host points somewhere reachable, then turn it back on.

.gitea/workflows/release.yml

@@ -17,6 +17,9 @@ jobs:
       - uses: actions/setup-go@v5
         with:
           go-version: "1.25.x"
+          # See build.yml: the runner's cache server is unreachable from job
+          # containers, so caching costs minutes of timeouts instead of saving.
+          cache: false
 
       - uses: goreleaser/goreleaser-action@v6
         with: