Removed forced string typing on attributeTypedCollectionHelper

This can technically be an integer, but it never will be in the context of our library.

Author: valzargaming

src/Discord/Parts/PartTrait.php

@@ -527,7 +527,7 @@ protected function attributeCollectionHelper($key, $class, ?string $discrim = 'i
      *
      * @return ExCollectionInterface
      */
-    protected function attributeTypedCollectionHelper(string $class, string $key): ExCollectionInterface
+    protected function attributeTypedCollectionHelper(string $class, $key): ExCollectionInterface
     {
         /** @var ExCollectionInterface $collection */
         $collection = $this->discord->getCollectionClass()::for($class);