Fix Taskbar existing app launch in DW

The issue: we were blocking the opening of existing app in when multi-instance flag was tunred on.

The Solution:  we don't actually need to do this since, the multiple taskbar icons of the same app are blocked pm TaskbarRecentsAppsController

Test: Manual, Presubmit
Bug: 391143101
Flag: EXEMPT bugfix
Change-Id: Ic2aa7cca4fd18d9b8cf48a2778c6e666241a4f7f