Rename ExpandableNotificationRow.setHeadsUpVisible to markHeadsUpSeen

The current method name is misleading, as it's sometimes called when the
notification is disappearing (from the start of the HUN outro animation).

Bug: 325936094
Flag: NONE only renaming a method
Test: build systemui
Change-Id: I382b73834d3334ce33a6ed3faa2949a2adc973dd
5 files changed