[FR]: Configure PR head branches to be automatically deleted after merged

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Describe the problem

Manual deletion of head branches is easy to forget.

### Describe the solution


### Additional context

[Here is the direct link to it.](https://github.com/android/nowinandroid/settings#merge_types_auto_merge)

### Code of Conduct

- [X] I agree to follow this project's Code of Conduct

Open the repository settings link in the issue and review the merge-related options shown there. Enable automatic deletion of merged pull request head branches, then verify that the setting is enabled and applies to merged pull requests.

Written by the indexing model from the issue text.