[build] pre-release PR should set to merge directly to trunk

Author: titusfortner

.github/workflows/pre-release.yml

@@ -91,6 +91,7 @@ jobs:
           author: Selenium CI Bot <[email protected]>
           delete-branch: true
           branch: release-preparation-${{ github.event.inputs.version }}
+          base: trunk
           title: "[build] Prepare for release of Selenium ${{ github.event.inputs.version }}"
           body: |
             **Warning: Manually update the changelogs before merging**