chore: update workflow to clean up branch (#6120)

Author: alicejli

.github/workflows/update-readme-table.yaml

@@ -20,6 +20,11 @@ jobs:
  with:
  python-version: '3.9'
 
+ - name: Delete existing 'update-readme-bot' branch
+ run: |
+ git push --delete origin update-readme-bot || echo "Branch doesn't exist, continuing..."
+ git branch -D update-readme-bot || echo "Branch doesn't exist, continuing..."
+
  - name: Install dependencies
  run: pip install pyyaml
 
@@ -34,8 +39,8 @@ jobs:
  git config --global user.email "cloud-java-bot@google.com"
  git add README.md
  git commit -m "chore: update README with release table"
- git checkout -b update-readme
- git push origin update-readme
+ git checkout -b update-readme-bot
+ git push origin update-readme-bot
 
  - name: Create Pull Request
  run: |