ISTWCMS-7163: use machine name so it gets the variable properly

src/Service/UwBlockAutoElements.php

@@ -712,7 +712,7 @@ class UwBlockAutoElements {
 
     // The number of publications to show form element.
     $form['publication_reference']['limit'] = $this->uwBlockService->getLimitPerBlockFormElement(
-      'publication reference',
+      'publication_reference',
       $config
     );