[TASK] Do not use ::class syntax for class tx_crawler_lib

This patch only pleases phpstan. The refactoring of the indexer
which includes the removal of the direct dependency to 3rd-party
classes is taken care of in the following issue.

https://forge.typo3.org/issues/83603

Releases: master
Resolves: #90384
Change-Id: Ia1ee984f692dce7f8293077cbea3359d6843cb46
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63261


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Tested-by: Björn Jacob <bjoern.jacob@tritum.de>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Björn Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>