Fix background color on tutorial success

Updating according to visd, not we don't change background color in tutorial after action success.
Also drive-by fix of title color in ActionTutorialScreen

Test: in light theme, complete tutorial and see nice background color vs very light background
Flag: com.android.systemui.shared.new_touchpad_gestures_tutorial
Bug: 309928033
Change-Id: Id17c9ae49d1200df77d9ab9978506681f205e73a