[TASK] Remove old default constants from TS service

$this->const in TemplateService and an extending class is super old,
unused and removed.

Resolves: #60561
Releases: 6.3
Change-Id: Ief7382b11d94094be587ae691ee6e3d1812b2d91
Reviewed-on: http://review.typo3.org/31803
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Benjamin Mack <benni@typo3.org>
Tested-by: Benjamin Mack <benni@typo3.org>