[TASK] Remove obsolete FormInlineAjaxController method

Protected controller method getErrorMessageForAJAX() is
unused since v7 and can be safely removed.

Resolves: #96828
Releases: main
Change-Id: I39e1229c8600ced151ddafdb982167b9d2ba2975
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/73421
Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Hader <oliver.hader@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Benni Mack <benni@typo3.org>

typo3/sysext/backend/Classes/Controller/FormInlineAjaxController.php

@@ -663,24 +663,6 @@ protected function removeFromArray($needle, $haystack, $strict = false)
         return $haystack;
     }
 
-    /**
-     * Generates an error message that transferred as JSON for AJAX calls
-     *
-     * @param string $message The error message to be shown
-     * @return array The error message in a JSON array
-     * @todo remove with TYPO3 v12.0
-     * @internal
-     */
-    protected function getErrorMessageForAJAX($message)
-    {
-        return [
-            'data' => $message,
-            'scriptCall' => [
-                'alert("' . $message . '");',
-            ],
-        ];
-    }
-
     /**
      * Get inlineFirstPid from a given objectId string
      *