Auto-merge options aren't properly updated when base repo changes

[alexr00]

1. Open a folder for a repo which you have push access too and which supports auto merge.
2. Have a git remote which you don't have push access to.
3. Make sure to include that remote in githubPullRequests.remotes
4. Create Pull Request
5. Change the base to a branch that belongs to the remote that you don't have push access to.
6. 🐛 The auto merge options is still in the "create" dropdown

// cc @benibenj