Tweak label creation logic on backport workflows (#6871)

* Tweak label creation logic on backport workflows

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

* Tweak label creation logic on backport workflows

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

---------

Signed-off-by: Peter Zhu <[email protected]>
(cherry picked from commit 801b6ec)
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]

Diff for: .github/workflows/backport.yml

@@ -42,9 +42,9 @@ jobs:
 
       - name: Label new backport PR with backport-automerge label
         run: |
-          PR_BRANCH=backport/backport-<%= number %>-to-<%= base %>
+          PR_BRANCH=backport/backport-${{ github.event.pull_request.number }}-to-`echo ${{ github.event.label.name }} | cut -d ' ' -f2`
           PR_NUMBER=`gh pr list -R opensearch-project/documentation-website --json "number,headRefName" --state open | jq -r ".[] | select(.headRefName == \"$PR_BRANCH\") | .number"`
-          echo "Update Backport PR #$PR_NUMBER on branch $PR_BRANCH with backport-automerge label"
+          echo "Update Backport PR '#$PR_NUMBER' on branch '$PR_BRANCH' with 'backport-automerge' label"
           gh issue edit -R opensearch-project/documentation-website $PR_NUMBER --add-label backport-automerge
         env:
-          GH_TOKEN: ${{ steps.github_app_token.outputs.token }}
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}