[BUGFIX] Avoid incomplete setup in FileHandlingUtilityTest

Since PHP 8.1 passing null as first argument
($format) has been deprecated. LanguageService
uses 'sprintf()' for  formatting messages.

In normal instances LanguageService would
return translated keys, or at least an empty
string.

Test in FileHandlingUtilityTest has been mocked
the LanguageServiceFactory to inject it into
a class, thus not providing a proper setup
LanguageService and return null instead of
an empty string as translation.

This patch change from mocked to prophezied
LanguageServiceFactory and LanguageServices
objects to avoid these deprecation messages
in PHP 8.1.

Resolves: #95740
Releases: master
Change-Id: I2a45cd9657c2e1e9f6d9e45d56dc398311b73d55
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/71943


Tested-by: core-ci <typo3@b13.com>
Tested-by: Simon Gilli <typo3@gilbertsoft.org>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Simon Gilli <typo3@gilbertsoft.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>