[BUGFIX] Callback in CrawlerHook of indexed_search sysext buggy

The property $callBack pointed to a Controller that was not existing.
Now it points back to the Hook.

Resolves: #50562
Releases: 6.2, 6.1, 6.0
Change-Id: I79e0ce73a23d98c5922ead43480202b3445282b2
Reviewed-on: https://review.typo3.org/22897
Reviewed-by: Stefan Neufeind
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn