Fix the notification content view alpha regression

Fixes the notification content view alpha regression caused by fixing
the alpha flicker during HUN appearing animation. We should limit the
reset of view sensitiveness and only do it when it's actually needed.

Fix: 342212697
Flag: com.android.systemui.notification_content_alpha_optimization
Test: atest PlatformScenarioTests:android.platform.test.scenario.sysui.notification.SensitiveNotificationProtectionWith50BigPictureNotificationsMicrobenchmark -- --test-arg com.android.tradefed.testtype.AndroidJUnitTest:device-listeners:android.device.collectors.UiInteractionFrameInfoListener,android.device.collectors.UiActionLatencyListener --module-arg PlatformScenarioTests:instrumentation-arg:iterations:=1 --module-arg PlatformScenarioTests:instrumentation-arg:drop-cache:=false --module-arg PlatformScenarioTests:instrumentation-arg:kill-app:=false
Change-Id: Iae24f6f09471a11ec428187b2a0aa96882c7dbf1