[BUGFIX] Remove invalid sort link in filelist module

Sorting in filelist happens via FAL drivers. Those are not capable of
sorting by TYPO3 References. The filelist nevertheless links and passes
the value _REF_ to FAL as sort option resulting in unpredictable results.

The _REF_ sort link has now been removed to avoid confusion.

Resolves: #61618
Releases: master, 9.5
Change-Id: Ie3cd46617cb7bafe0ae6d8c4252e52c11a4c98d7
Reviewed-on: https://review.typo3.org/c/59895
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Guido Schmechel <guido.schmechel@brandung.de>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Guido Schmechel <guido.schmechel@brandung.de>
Reviewed-by: Benni Mack <benni@typo3.org>

typo3/sysext/filelist/Classes/FileList.php

@@ -502,6 +502,8 @@ public function getTable($rowlist)
                         $cells[] = '<a class="btn btn-default" rel="" href="#" onclick="' . htmlspecialchars($onClick) . '" title="' . htmlspecialchars($this->getLanguageService()->getLL('clip_markRecords')) . '">' . $this->iconFactory->getIcon('actions-document-select', Icon::SIZE_SMALL)->render() . '</a>';
                     }
                     $theData[$v] = implode('', $cells);
+                } elseif ($v === '_REF_') {
+                    $theData[$v] = htmlspecialchars($this->getLanguageService()->getLL('c_' . $v));
                 } else {
                     // Normal row:
                     $theT = $this->linkWrapSort(htmlspecialchars($this->getLanguageService()->getLL('c_' . $v)), $this->folderObject->getCombinedIdentifier(), $v);