Remove all the closing tasks.

In some cases of core based close transitions, there can be multiple
tasks in desktop that are closing. Handle removal of all of them
insteado of just one of them.

Fix: 414258638
Test: atest DesktopTasksTransitionObserver
Flag: com.android.window.flags.enable_desktop_close_task_animation_in_dtc_bugfix
Change-Id: I1b46f6df530fa1c8bdd859eabefacebedb53d259