Removes the A11y tutorial that displays on change to gesture navigation

Switching to gesture navigation puts button mode in FAB,
so there's no longer a need to show a gesture tutorial.

Test: change navigation modes. Verify no tutorial is shown for either option
Flag: android.provider.a11y_standalone_gesture_enabled
Bug: 371027085
Change-Id: I71e33efea3e25d22b0bc41c33b17de11f9ef2d64