[!!!][TASK] Remove obsolete HtmlParser methods

Some now unused methods (after the XHTML cleanup)
within HtmlParser can be removed as well.

Resolves: #72667
Releases: master
Change-Id: I164505001d76db9b3e111d466f7b823e5cfe6b65
Reviewed-on: https://review.typo3.org/45854


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>