MDL-76725 mod_wiki: avoid named arguments in real path callback.

See also f4fb91ae. PHP8 now supports named arguments in calls to
the `call_user_func_array` method, which can result in differing
behaviour compared to PHP7, e.g. in this case it was throwing an
exception due to an unknown named parameter.

mod/wiki/parser/markups/wikimarkup.php

@@ -332,7 +332,7 @@ abstract class wiki_markup_parser extends generic_parser {
 
     protected function real_path($url) {
         $callbackargs = array_merge(array($url), $this->realpathcallbackargs);
-        return call_user_func_array($this->realpathcallback, $callbackargs);
+        return call_user_func_array($this->realpathcallback, array_values($callbackargs));
     }
 
     /**