Location Consent & undo Remeber This Setting
geffchang's answer is correct. That said, it is meant for a rooted Android so users of non-rooted Android devices may not find it of much use.

Those users, if willing to sacrifice third-part apps' data associated with their Google account, can consider clearing data of Play services' app as a solution. 

Set location mode to Device only for once, disable location mode, launch Settings app &rarr; Apps &rarr; All apps &rarr; Google Play services &rarr; Force stop &rarr; Manage Space &rarr; Clear data &rarr; Force stop again &rarr; optionally reboot.

Now try enabling the location mode. It should default to Device only and should you attempt to change to High accuracy, that Improve location accuracy? dialog for agreement would be shown to you.