ci: golangci-lint-action v7, drop kubebuilder e2e stub

- golangci-lint-action v6 does not support golangci-lint v2, bump to v7
- remove test-e2e.yml kubebuilder stub — e2e requires OCI environment,
  nightly-e2e.yml covers scheduled runs

Author: syscod3

.github/workflows/ci.yml

@@ -38,7 +38,7 @@ jobs:
           git diff --exit-code || (echo "Run 'make manifests' and commit the result" && exit 1)
 
       - name: golangci-lint
-        uses: golangci/golangci-lint-action@v6
+        uses: golangci/golangci-lint-action@v7
         with:
           version: v2.8.0