Revert "Fix ClassCastException in QuickstepModelDelegate"

This reverts commit 380f8fd89016b2527d9a3fb2b35c0c4810e12855.

Reason for revert: remove bug fix on master

Bug: 173838775
Change-Id: I3cbb3e383c52095a10b3e22ea4c586c0c3c8d7a9
5 files changed