chore(core) rm Feature::RequestRule (#11866)

## Summary
This feature is now reasonably stable, let's remove it so we can
simplify our upcoming iterations here.

## Testing 
- [x] Existing tests pass

codex-rs/app-server/tests/suite/send_message.rs

@@ -477,7 +477,6 @@ fn assert_permissions_message(item: &ResponseItem) {
                 &SandboxPolicy::DangerFullAccess,
                 AskForApproval::Never,
                 &Policy::empty(),
-                false,
                 &PathBuf::from("/tmp"),
             )
             .into_text();