[Imaging Uploader] Use Utility::getMaxUploadSize() instead of ini_get (…

…#4367)

Makes error message consistent with upload size limit that's displayed on the front-end in the case where `post_max_size != upload_max_filesize`

modules/imaging_uploader/php/imaging_uploader.class.inc

@@ -121,7 +121,7 @@ class Imaging_Uploader extends \NDB_Menu_Filter_Form
         if (empty($_FILES) && empty($_POST)
             && ($_SERVER['REQUEST_METHOD']=='POST')
         ) { //catch file overload error...
-            $upload_max_size = ini_get('upload_max_filesize');
+            $upload_max_size = \Utility::getMaxUploadSize();
             $error_message   = "Please make sure files are not larger than " .
                                 $upload_max_size;
             http_response_code(400);