refactor(neuron): remove return type hint from __get method

src/Libs/Neuron.php

@@ -52,7 +52,7 @@ class Neuron
      * @param  string $index The name of the property being accessed.
      * @return null   Always returns null for undefined properties.
      */
-    public function __get(string $index): null
+    public function __get(string $index)
     {
         return null;
     }