[BUGFIX] Suppress deprecation in EmptyFileSearchResult

Since PHP 8.1 The Countable interface has tentative
return types. This means mismatching return types
trigger deprecation notices. The methods current
and key of EmptyFileSearchResult have the mismatching
return type void. To suppress the deprecation
without a breaking change, the #[\ReturnTypeWillChange]
attribute has been added to those methods.

Resolves: #95758
Releases: master
Change-Id: I3b8c75fa754762904277c88c9fbf9a8d72dc4ba4
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/71964


Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>