[TASK] Replace usage of GeneralUtility::milliseconds in Indexer

Replace the usage of `GeneralUtility::milliseconds` in Indexer class
which has been deprecated with 91001.

Resolves: #91192
Releases: master
Change-Id: I2057ecec038195d67acab10946d4542b1fba9646
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/64316


Tested-by: Josef Glatz <josefglatz@gmail.com>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Josef Glatz <josefglatz@gmail.com>
Reviewed-by: Benni Mack <benni@typo3.org>