Keep the animateItem modifier but remove the placementSpec on selected tiles

Removing the animateItem spec caused the tile to lose track of previous positions in the grid if we quickly unselected and moved, such as when we're undoing a move.
Keeping the animateItem modifier at all times keeps track of that offset while still stopping the tiles from animating when we don't want it to.

Test: manually undoing tile moves
Flag: com.android.systemui.qs_ui_refactor_compose_fragment
Fixes: 413527151
Change-Id: I922cc3fb26b9af3a75ee3b5eebd7363e3f101c12