Updated EAV Attribute code max lenght

 - EAV attribute code will be transformed into column name for flat tables. MySQL does not support column name with more than 64 symbols

Author: Oleksii Korshenko

app/code/Magento/Eav/Model/Entity/Attribute.php

@@ -23,7 +23,7 @@ class Attribute extends \Magento\Eav\Model\Entity\Attribute\AbstractAttribute im
     /**
      * Attribute code max length
      */
-    const ATTRIBUTE_CODE_MAX_LENGTH = 255;
+    const ATTRIBUTE_CODE_MAX_LENGTH = 60;
 
     /**
      * Cache tag