ci: stop waiting ~9 minutes on an unreachable cache

Validate took ~10 minutes, of which ~10 seconds was work: setup-go's
cache restore and save each waited ~4.7 minutes for a connect timeout,
because the runners' built-in cache server sits on a network job
containers can't reach. Turn off setup-go caching (three small modules
aren't worth it) and the game-test runner's cache server, so any cache
step skips at once.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitea/workflows/validate.yml

@@ -30,6 +30,9 @@ jobs:
         uses: actions/setup-go@v5
         with:
           go-version-file: go.mod
+          # Three small modules aren't worth caching, and the runners' cache server is unreachable
+          # from job containers: each restore/save attempt timed out after ~4.7 minutes.
+          cache: false
 
       - name: Validate
         run: |
@@ -69,6 +72,9 @@ jobs:
         uses: actions/setup-go@v5
         with:
           go-version-file: go.mod
+          # Three small modules aren't worth caching, and the runners' cache server is unreachable
+          # from job containers: each restore/save attempt timed out after ~4.7 minutes.
+          cache: false
 
       # Secrets named in a game's test.yaml must be listed here to reach the boot test
       - name: Boot test changed games
@@ -93,6 +99,9 @@ jobs:
         uses: actions/setup-go@v5
         with:
           go-version-file: go.mod
+          # Three small modules aren't worth caching, and the runners' cache server is unreachable
+          # from job containers: each restore/save attempt timed out after ~4.7 minutes.
+          cache: false
 
       # Unlike the node-agent notify, a failure here fails the run, because the panel would
       # otherwise keep serving the previous templates silently.