Remove custom timeout logic from hub v2

In v2, we can let PowerManagerService handle the timeout behavior since
we no longer keep the dream active underneath the hub.

Bug: 394915563
Test: atest CommunalSceneStartableTest
Flag: com.android.systemui.glanceable_hub_v2
Change-Id: I24d7db4c09e17a4852cbc9d842352904ba4527fc