Clicking `delete source branch` does nothing.

Summary

Using the merge when pipeline succeeds without checking the delete source branch causes the branch to not be deleted once the MR is merged. (This is desired) This bug occurs once the merge is set to automatically merge, but the user decides to delete the source branch afterwards.

Clicking the "Delete source branch" does not update the UI language and it continues to say the source branch will not be deleted

Before clicking:

After clicking the delete source branch:

Steps to reproduce

1. Create a merge request
2. Approve the merge request
3. Set the merge request to automatically merge without deleting the source
4. Click delete source branch
5. Observe that nothing happens (the language doesnt change and the branch isn't deleted once merged)

What is the expected correct behavior?

The branch should automatically delete once the branch has merged if the button is clicked to delete the source branch afterwards.