How to Manage the System Group Submission Policy in SharePoint 2013

Hello all,

I want to restrict the users in case of Entering the Enterprise Keywords in the Ask About me In the Mysite in SharePoint 2013.

I am trying to change the Submission Policy form Open to close for the Keyword {Term set} in System {group}

But I couldn't able to change this option even though particular user have manager permissions.

Thanks in Advance,