Remove pending launch cookie listeners

- Hypothetical scenario, if a pending launch-cookie task listener
  is added and removed immediately before the task appears (or before
  the next task info changed if the pending launch cookie is set for
  and existing task), then the listener is not removed from the
  cookie-listener map, and we may still attempt to migrate the
  listener on the next event, which can conflict with the caller's
  next listener for the given task.

Bug: 427188589
Flag: EXEMPT bugfix
Test: atest ShellTaskOrganizerTests
Change-Id: I54ecd66ef04a2ccd7cd93c11e9d6ebaa19a64b88