[TASK] Disable PHP 8 functional testing

The recent extbase related class schema revert
introduced a warning within functional PHP 8
tests leading to test fails.
Run the mariadb functionals with PHP 7.4 instead
of PHP 8 for the moment again.
Additionally a minor type hint from one of the
recent security patches is added in ext:form
area to make phpstan happy again.

Related: #93745
Resolves: #93751
Releases: master
Change-Id: Idac9c953d7029c3f67d6d1060354edfa5fa972dc
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/68463


Tested-by: core-ci <typo3@b13.com>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>

Build/gitlab-ci/pre-merge/functional.yml

-functional mariadb 10.3 php 8.0 pre-merge:
+functional mariadb 10.3 php 7.4 pre-merge:
   stage: main
   except:
     refs:
@@ -6,8 +6,8 @@ functional mariadb 10.3 php 8.0 pre-merge:
       - master
   parallel: 10
   script:
-    - Build/Scripts/runTests.sh -s composerInstall -p 8.0
-    - Build/Scripts/runTests.sh -s functional -d mariadb -i 10.3 -p 8.0 -c $CI_NODE_INDEX/$CI_NODE_TOTAL
+    - Build/Scripts/runTests.sh -s composerInstall -p 7.4
+    - Build/Scripts/runTests.sh -s functional -d mariadb -i 10.3 -p 7.4 -c $CI_NODE_INDEX/$CI_NODE_TOTAL
 
 functional postgres 10 php 7.4 pre-merge:
   stage: main

typo3/sysext/form/Classes/Domain/Finishers/DeleteUploadsFinisher.php

@@ -72,6 +72,7 @@ class DeleteUploadsFinisher extends AbstractFinisher
     protected function deleteEmptyUploadFolders(array $folders): void
     {
         foreach ($folders as $folder) {
+            /** @var Folder $parentFolder */
             $parentFolder = $folder->getParentFolder();
 
             if ($this->isEmptyFolder($folder)) {