Revert "Expose ACTION_USER_SWITCHED as system API"

This reverts commit ffe0cbe5ca68b7c8fa939106ef39c71eccc10f13.

Reason for revert: Not needed for now; will be redone in S.

Bug: 148180958
Change-Id: I426e00e1eb79af5b520fc8c59439614459720fa6
2 files changed