refactor: fix incorrect return value

See https://www.php.net/manual/en/language.oop5.overloading.php#language.oop5.overloading.members

Author: kenjis

system/Entity/Entity.php

@@ -429,7 +429,7 @@ public function cast(?bool $cast = null)
      *
      * @param array|bool|float|int|object|string|null $value
      *
-     * @return $this
+     * @return void
      *
      * @throws Exception
      */
@@ -452,16 +452,14 @@ public function __set(string $key, $value = null)
         if (method_exists($this, $method)) {
             $this->{$method}($value);
 
-            return $this;
+            return;
         }
 
         // Otherwise, just the value. This allows for creation of new
         // class properties that are undefined, though they cannot be
         // saved. Useful for grabbing values through joins, assigning
         // relationships, etc.
         $this->attributes[$dbColumn] = $value;
-
-        return $this;
     }
 
     /**