TaskOrganizer: Send newest TaskInfo in taskVanished

When leaving PIP SysUI might need to know the target mode
and bounds to animate correctly. taskInfoChanged may
not have yet been dispatched though. A simple solution is
to provide the info in TaskVanished.

Bug: 150716630
Test: Existing tests pass
Change-Id: I871f745198d6b4bc92cc5701128c5489c154f4f9