Tweak backport branch delete workflow to delete other merged branches (#6809)

* Tweak backport branch delete workflow to delete other merged branches

Signed-off-by: Peter Zhu <[email protected]>

* Add prevent condition due to SvanBoxel/delete-merged-branch#204 issues

Signed-off-by: Peter Zhu <[email protected]>

---------

Signed-off-by: Peter Zhu <[email protected]>

Author: peterzhuamazon

Diff for: .github/workflows/delete_backport_branch.yml

@@ -0,0 +1,22 @@
+name: Delete merged branch of the PRs
+on:
+  pull_request:
+    types:
+      - closed
+
+jobs:
+  delete-branch:
+    runs-on: ubuntu-latest
+    if: |
+      startsWith(github.event.pull_request.head.repo.full_name, 'opensearch-project/documentation-website') &&
+      startsWith(! github.event.pull_request.head.ref, 'main') &&
+      startsWith(! github.event.pull_request.head.ref, '1.') &&
+      startsWith(! github.event.pull_request.head.ref, '2.') &&
+      startsWith(! github.event.pull_request.head.ref, 'version/')
+    steps:
+      - name: Echo remove branch
+        run: echo Removing ${{github.event.pull_request.head.ref}}
+      - name: Delete merged branch
+        uses: SvanBoxel/delete-merged-branch@main
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}