Disable MULTI_DB_GRID_MIRATION_ALGO

This seems to be incomplete, breaking custom
workspace order on upgrade or grid size change.

Test: m, observe upgrading from previous android
      version doesn't break custom workspace and
      changing grid sizes works properly, including
      grid preview in ThemePicker.

Change-Id: Iee4cb6eb498d7bd3cd56e0c0b73cda1d42f5a3f1