[TASK] Add unit test to cover prefixComment

Add unit test to cover ContentObjectRenderer::prefixComment

Resolves: #80526
Releases: master
Change-Id: I37e89ecfdb2cea2f9290eced97337c0019e78ba9
Reviewed-on: https://review.typo3.org/52219


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
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>