Bump korthout/backport-action from 3.4.1 to 4.0.0

Bumps [korthout/backport-action](https://github.com/korthout/backport-action) from 3.4.1 to 4.0.0.
- [Release notes](https://github.com/korthout/backport-action/releases)
- [Commits](d07416681c...3634249d41)

---
updated-dependencies:
- dependency-name: korthout/backport-action
  dependency-version: 4.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/backbot.yml

@@ -44,7 +44,7 @@ jobs:
           sha: ${{ github.event.pull_request.head.sha }} # Checkout the latest commit of the merged PR.
 
       - name: Run Backbot
-        uses: korthout/backport-action@d07416681cab29bf2661702f925f020aaa962997 # v3.4.1
+        uses: korthout/backport-action@3634249d418881baa47fd6bae694506145f7a61b # v4.0.0
         with:
           github_token: ${{ steps.backbot-token.outputs.token }}
           copy_labels_pattern: '^(?!cla-signed$).*' # copy all labels other than the cla-signed label