Wrong commit is checked out when local branch exists with the same name

[parched]

• Extension version: 0.116.2
• VSCode Version: 1.103.2
• OS: Windows
• Repository Clone Configuration (single repository/fork of an upstream repository):
• GitHub Product (GitHub.com/GitHub Enterprise version x.x.x):

Steps to Reproduce:

1. Create local branch called my-branch
2. Create an unrelated PR with an upstream source branch called my-branch
3. Click the Checkout Pull Request button
4. Note the commit checked out is the local my-branch not the remote one.