[TASK] Deprecate ClientUtility

The class ClientUtility is outdated and not used anymore and can be
deprecated.

Resolves: #82903
Releases: master
Change-Id: I616b4518bfebac8239ecca0b48cad1b037c0ba6d
Reviewed-on: https://review.typo3.org/54538


Reviewed-by: Jigal van Hemert <jigal.van.hemert@typo3.org>
Tested-by: Jigal van Hemert <jigal.van.hemert@typo3.org>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>