This PR removes onboarding modals for features that were announced, at
this point, a long time ago: Git v1, Debugger, and Agent Panel v1. This
cleans up the actions list a bit when you search for "onboarding". I
left the ACP and Claude Code ones, though; they were the two more recent
ones, but we should be able to remove them soon enough, too.
Release Notes:
- N/A