I am trying to upgrade magento version from 2.1.9 to 2.1.10

I got following error.

Module 'Magento_Ui' from '/home/zitomer/upgrade.zitomer.com/app/code/Magento/Ui' has been already defined in '/home/zitomer/upgrade.zitomer.com/vendor/magento/module-ui'.

How to resolve this error as I am not able to upgrade on 2.1.10