[Dual Shade] Remove DualShade scrim transparency in ScrimController.

Bug: 388793191
Test: Manually by expanding/collapsing the shade in both scene container
 on and off modes, an observing that the scrim fades in/out as expected.
Test: Unit tests still pass.
Flag: com.android.systemui.scene_container
Change-Id: Ie7a9c673d48a09b7afed7c4541917f0ce6f1562a