• Extension version: v0.68.0
• VSCode Version: 1.80.0-insider
• OS: macOS 13.4.1

Steps to Reproduce:

1. Open a diff from the extension when there are multiple files in the diff. Make sure you're not in the first file of the pull request.
2. Run the "Go to previous diff in pull request" command when focused on the first diff in a file.

I believe this has to do with this line: https://github.com/microsoft/vscode-pull-request-github/blob/main/src/commands.ts#L1371. When going to the previous request, the extension should use reviewManager.reviewModel.localFileChanges.length - 1 - i instead of reviewManager.reviewModel.localFileChanges.length - 1.