[TASK] Remove unneeded `$siteMockRevelation` in SiteResolvingTest

With migration away from prophecy during v12 development, the variable
`$siteMockRevelation` is not needed anymore as phpunit mocks don't know
the concept of revelations.

Resolves: #103958
Releases: main, 12.4
Change-Id: I92497737dfbba3ef1cd99e4fbd96751e00057a16
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/84449


Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Kevin Appelt <kevin.appelt@icloud.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Oliver Bartsch <bo@cedev.de>