Ensure Desktop Tasks show up in Taskbar multi instance menu

This change adds in desktop tasks to show up in the Manage Windows
Taskbar menu. Previously these were getting filtered out.

Fix: 380167542
Bug: 315989246
Test: Launch multiple tasks in desktop mode and see that they show up in
the multi instance viewer from the Taskbar menu
Flag: com.android.launcher3.enable_multi_instance_menu_taskbar

Change-Id: Ia07b3ad68f43c0f121b0608c5341d50970c8af4c