Tweak syntax for the merged branch deletion workflow (#6814)

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

Author: peterzhuamazon

Diff for: .github/workflows/.delete_backport_branch.yml.swp

@@ -9,10 +9,10 @@ jobs:
     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/')
+      ${{ !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}}