feat(workflow): add push trigger to test-upgrade-legacy workflow

- Add push trigger to the GitHub Actions workflow for test-upgrade-legacy
- Ensure workflow runs on push events to the main branch

Author: CoMfUcIoS

.github/workflows/test-upgrade-legacy.yaml

@@ -23,6 +23,7 @@ on:
       - .puppet-lint.rc
       - .fixtures.yml
     branches: [main]
+  push:
   workflow_dispatch:
     inputs:
       ssh-debugging: