Edits to comments on PRs not being applied

[stuartleeks]

Found while testing #2722 (repo opened via Remote-Repositories)

• Extension version: v2021.7.39424 (nightly)
• VSCode Version: 1.59.0-insider (user setup)
• OS: Windows_NT x64 10.0.19043

Steps to Reproduce:

1. View a PR and add a comment
   

2. Click the edit button and edit the comment
   

3. Click save
   

Note that the comment has reverted to the original value. Checking via github.com the PR still shows the original comment