CI: Remove pr-commands-closed workflow as replaced with auto-milestone (#72793)

.github/workflows/pr-commands-closed.yml

@@ -1,20 +0,0 @@
-name: Run when PRs are closed
-on:
-  pull_request:
-    types:
-      - closed
-concurrency:
-  group: pr-commands-closed-${{ github.event.number }}
-jobs:
-  close_job:
-    permissions:
-      pull-requests: write
-    # this job will only run if the PR has been closed without being merged
-    if: github.event.pull_request.merged == false
-    runs-on: ubuntu-latest
-    steps:
-    - run: |
-        echo PR #${{ github.event.number }} has been closed without being merged, removing milestone.
-        gh pr edit ${{ github.event.number }} --milestone "" --repo $GITHUB_REPOSITORY
-      env:
-        GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}