Settings: remove force overflow button

As of KitKat, the overflow button is always shown regardless of if
a physical menu button is present or not.

https://android.googlesource.com/platform/frameworks/base.git/+/ea04f3cfc6e245fb415fd352ed0048cd940a46fe

Change-Id: Ia05756248e9f55ac68bf31abdb7327edf6a806c4