ACP2E-156: Merchants can create custom attribute, but it causes an error when trying to save an entity account

- code style

Author: o-dubovyk

app/code/Magento/Catalog/Model/Product/ReservedAttributeCheckerAdapter.php

@@ -22,7 +22,7 @@ class ReservedAttributeCheckerAdapter implements ReservedAttributeCheckerInterfa
     /**
      * @var ReservedAttributeList
      */
-    protected $reservedAttributeList;
+    private $reservedAttributeList;
 
     /**
      * @param ReservedAttributeList $reservedAttributeList