ci: disable setup-go cache to skip 4m Gitea cache server timeout

The action tries to restore from 172.18.0.2:36061 (Gitea's cache
server), times out, falls through to a fresh download anyway. Pure
waste since the runner already has the toolchain in
/opt/hostedtoolcache. Turn cache off.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.gitea/workflows/e2e.yml

@@ -30,7 +30,7 @@ jobs:
         uses: actions/setup-go@v5
         with:
           go-version: "1.26.x"
-          cache: true
+          cache: false
 
       - name: Install live-image build dependencies
         run: |