[TASK] Remove unneeded SingletonInstance resets in recent extbase tests

These were introduced with the recent extbase configuration manager
hardening but are not needed, because there are no singletons
triggered via makeInstance in these tests.

Change-Id: Iae4d55acd8a02997dd8fc256231c39503a8cfc88
Resolves: #88693
Related: #87628
Releases: master
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/61234


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Alexander Schnitzler <review.typo3.org@alexanderschnitzler.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Alexander Schnitzler <review.typo3.org@alexanderschnitzler.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>