Find and remove visible task onTaskVanished.

When a task vanishes, its displayId is set to INVALID_DISPLAY. Find the
display that we put the task in as visible and remove it from the
visibleTasks list.

Bug: 323162330
Test: atest DesktopModeTaskRepositoryTest
Change-Id: Ib036ae0eea4754fd5071d92fba74f1d98f5fcbcb
2 files changed