[TASK] Replace misuse of parent keyword to $this

The parent keyword is misused in some places and $this can be
used instead.

Resolves: #95199
Releases: master
Change-Id: I79f7bd041c46210fa1961a93326b02137dcc7abe
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/71042


Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Jochen <rothjochen@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Jochen <rothjochen@gmail.com>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>