Trim upstream-specific workflows + CODEOWNERS

Drop workflows we don't need on the fork:
- licensed.yml (no .licenses for @google-cloud/storage)
- workflow.yml (jest tests mock @actions/cache, break with wrapper)
- close-inactive-issues, issue-opened, pr-opened (upstream oncall)
- publish-immutable-actions (not publishing to marketplace)
- release-new-action-version (replaced by auto-tag.yml)

Drop CODEOWNERS so merges don't require @actions/actions-cache review.
Drop .licensed.yml config (no longer used).

.github/workflows/close-inactive-issues.yml

@@ -1,23 +0,0 @@
-name: Close inactive issues
-
-on:
-  schedule:
-    - cron: "30 8 * * *"
-
-jobs:
-  close-issues:
-    runs-on: ubuntu-latest
-    permissions:
-      issues: write
-      pull-requests: write
-    steps:
-      - uses: actions/stale@v9
-        with:
-          days-before-issue-stale: 200
-          days-before-issue-close: 5
-          stale-issue-label: "stale"
-          stale-issue-message: "This issue is stale because it has been open for 200 days with no activity. Leave a comment to avoid closing this issue in 5 days."
-          close-issue-message: "This issue was closed because it has been inactive for 5 days since being marked as stale."
-          days-before-pr-stale: -1
-          days-before-pr-close: -1
-          repo-token: ${{ secrets.GITHUB_TOKEN }}