Fix issue with drop target when dragging new widget.

The math used to calculate the drop target when dragging a widget from
the widget picker needed a tweak.

Bug: 347291755
Test: Manually by dragging widgets from the widget picker.
Flag: com.android.systemui.communal_hub
Change-Id: If1d8f96fe87ac61b7ace706f24b82edb7a249c9b
2 files changed