[Dual Shade] Ensure the Notifications Shade clock is start-aligned.

It currently occupies the full width, which results unintentionally in
center alignment for custom clocks.

Fix: 397919736
Test: Manually by opening the notifications shade on both narrow and
 wide screens.
Test: Existing unit tests still pass.
Flag: com.android.systemui.scene_container
Change-Id: Ia8a7dc7e2d6d5f45c3baccf955ce92bf33aa79cf