* Remove obsolete comment

The method `_stopCursorTimer` no longer exists.

* Add edited comment back in

Addresses these comments:
- https://github.com/flutter/flutter/pull/120265#discussion_r1101673834
- https://github.com/flutter/flutter/pull/120265#discussion_r1102120022

---------
Co-authored-by: Kate Lovett <katelovett@google.com>