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/licensed.yml

@@ -1,43 +0,0 @@
-name: License check
-
-on:
-  push:
-    branches:
-      - main
-  pull_request:
-    branches:
-      - main
-  workflow_dispatch:
-
-permissions:
-  contents: read
-
-jobs:
-  validate-cached-dependency-records:
-    runs-on: ubuntu-latest
-    name: Check licenses
-    steps:
-
-      - name: Checkout
-        uses: actions/checkout@v5
-
-      - name: Install dependencies
-        run: npm ci --ignore-scripts
-
-      - name: Set up Ruby
-        uses: ruby/setup-ruby@v1
-        with:
-          ruby-version: '3.1.7'
-
-      - name: Install licensed tool
-        run: |
-          cd "$RUNNER_TEMP"
-          curl -Lfs -o licensed.tar.gz https://github.com/licensee/licensed/archive/refs/tags/v5.0.4.tar.gz
-          tar -xzf licensed.tar.gz
-          cd licensed-5.0.4
-          bundle install
-
-      - name: Check cached dependency records
-        run: |
-          cd ${{ github.workspace }}
-          BUNDLE_GEMFILE=$RUNNER_TEMP/licensed-5.0.4/Gemfile bundle exec $RUNNER_TEMP/licensed-5.0.4/exe/licensed status