Fix: remove incompatible return type (#2517)

* Fix: remove incompatible return type

* fix: remove return type for addCastAttributesToArray

---------

Co-authored-by: Divine <48183131+divine@users.noreply.github.com>

Author: saulens22

src/Eloquent/Model.php

@@ -187,7 +187,7 @@ protected function getAttributeFromArray($key)
     /**
      * @inheritdoc
      */
-    public function setAttribute($key, $value): static
+    public function setAttribute($key, $value)
     {
         // Convert _id to ObjectID.
         if ($key == '_id' && is_string($value)) {
@@ -518,7 +518,7 @@ public function __call($method, $parameters)
     /**
      * @inheritdoc
      */
-    protected function addCastAttributesToArray(array $attributes, array $mutatedAttributes): array
+    protected function addCastAttributesToArray(array $attributes, array $mutatedAttributes)
     {
         foreach ($this->getCasts() as $key => $castType) {
             if (! Arr::has($attributes, $key) || Arr::has($mutatedAttributes, $key)) {