Revert "copilot: Fix vision request detection for follow-up messages" (#31776)

Reverts zed-industries/zed#31760

see this comment for context:
https://github.com/zed-industries/zed/pull/31760#issuecomment-2923158611.

Release Notes:

- N/A
a539a38f13Umesh Yadav committed on 5/30/2025, 7:28:31 PM· committed by GitHubparentca6fd10
1 file changedLine totals unavailable