[flexiglass] Relocate call to HeadsUpManager.unpinAll

Adding back in a side effect of HUN snooze that had to be dropped in the initial CL because it was causing a flicker and tracking loss. Now it is called after the touch handoff, and isHeadsUpAnimatingAway is populated correctly.

Bug: 340514839
Test: verified via logging that as a HUN is dragged upwards, HeadsUpManager marks it as unpinned and sets isHeadsUpAnimatingAway as true.
Flag: com.android.systemui.scene_container
Change-Id: I75d98d52fe6b83cf69f299ee6e41f9cfebbc0bce