[Duo Chat] Stop sending additional context to older gitlab instances

Checklist

• I'm using the latest version of the extension (see the latest version in the right column of this page)
  • Extension version: Put your extension version here
• I'm using the latest VS Code version (find the latest version here)
  • VS Code version: Put your VS Code version here
• I'm using a supported version of GitLab (see README for the supported version)
  • GitLab version: Put your GitLab version here, or say "happens on gitlab.com"

Summary

Steps to reproduce

Although any questions I ask are not answered. At that time, I see an error pop-up with message API error: AiAdditionalContextInput isn't a defined input type (on $additionalContext). On logs all I see are 200 response.

What is the current bug behavior?

I see an error pop-up with message `API error: AiAdditionalContextInput isn't a defined input

What is the expected correct behavior?

The invalid field isn't submitted to older GitLab instances.

Relevant logs and/or screenshots

Possible fixes