Make newPivotQuery function public

PR laravel/framework#31677 made newPivotQuery function public and that's the reason why builds are failing.

Author: divine

src/Jenssegers/Mongodb/Relations/BelongsToMany.php

@@ -265,7 +265,7 @@ protected function buildDictionary(Collection $results)
     /**
      * @inheritdoc
      */
-    protected function newPivotQuery()
+    public function newPivotQuery()
     {
         return $this->newRelatedQuery();
     }