Revert "[2/2] Buttons: Switch to last app"

This reverts commit 28a56e956858ac62a8dc6e50972f03c22cd3d86b.

Change-Id: I588372515272c416281c379d55ff56e39b3deb8b
Settings: add last app action to be assigned to hardware keys

Change-Id: I9004412528a7c32fecd7edea6167c1b80c51730d
Signed-off-by: Roman Birg <roman@cyngn.com>