Different Attempt on UML Automation

[wd60622]

Trying a different trigger which has different permissions

Reference:

• https://docs.github.com/en/actions/writing-workflows/choosing-when-your-workflow-runs/events-that-trigger-workflows#running-your-pull_request_target-workflow-when-a-pull-request-merges

[juanitorduz]

Let's try it out!