Disable 'Allow editing commits feature' if 'Reject unsigned commit' options is enabled

#292493 (closed) prevents a user from enabling "Allow editing commits" if "Reject unsigned commit" options is enabled at project-level.

We might need to take care of the opposite case by preventing "Reject unsigned commits" to be enabled if "Allow editing commits feature" is enabled. An alternative could be to automatically disable "Allow editing commits" if the user enables "Reject unsigned commits".