chore(config) rm Feature::CodexGitCommit (#22412)

## Summary
Removes the unused Feature::CodexGitCommit

## Testing
- [x] tests pass

codex-rs/thread-manager-sample/src/main.rs

@@ -196,7 +196,6 @@ fn new_config(model: Option<String>, arg0_paths: Arg0DispatchPaths) -> anyhow::R
         include_skill_instructions: false,
         include_environment_context: false,
         compact_prompt: None,
-        commit_attribution: None,
         notify: None,
         tui_notifications: TuiNotificationSettings::default(),
         animations: true,