Merge pull request #7451 from ping-yee/docs-replace-filter

docs: fix PHPDoc types in `Filter` class.

system/Filters/Filters.php

@@ -375,7 +375,7 @@ public function enableFilters(array $names, string $when = 'before')
     /**
      * Returns the arguments for a specified key, or all.
      *
-     * @return mixed
+     * @return array<string, string>|string
      */
     public function getArguments(?string $key = null)
     {