copilot: Only set Copilot-Vision-Request header for vision requests (#33552)
Closes #31951
The fix is copied and translated from copilot chat actual implementation
code:
https://github.com/microsoft/vscode-copilot-chat/blob/ad7cbcae9a964e8efb869bf1426999e56ea63cf0/src/platform/openai/node/fetch.ts#L493C1-L495C3
Release Notes:
- Fix copilot failing due to missing `Copilot-Vision-Request` from
request.
5fbb7b0d40Umesh Yadav committed on 6/27/2025, 7:37:26 PM· committed by GitHubparentf12b0dd