Add a workaround in automatic rebase workflow to continue on error (#18176)

.github/workflows/rebase.yml

@@ -23,6 +23,7 @@ jobs:
         fetch-depth: 0
     - name: Post rebase started comment to pull request
       uses: actions/github-script@v6
+      continue-on-error: true
       with:
         script: |
           const backport_start_body = `Started rebase: https://github.com/${context.repo.owner}/${context.repo.repo}/actions/runs/${process.env.GITHUB_RUN_ID}`;