[TASK] RTE: Remove ExtJS QuickTips from status bar

This completes the migration of the RTE status bar to plain JavaScript.

Releases: master
Resolves: #63957
Change-Id: I7b0a2e08d57c21e6a8c4325ec5fb456d15bc4371
Reviewed-on: http://review.typo3.org/35543
Reviewed-by: Stanislas Rolland <typo3@sjbr.ca>
Tested-by: Stanislas Rolland <typo3@sjbr.ca>