Adjust unit tests following behavior change from b9df0ebc.

Since commit b9df0ebc, ActivityRecord no longer adjusts the task order
when finishing an activity. Instead, the order will change when
resuming the next activity, if necessary.

Flag: com.android.window.flags.polish_close_wallpaper_includes_open_change
Bug: 421436197
Test: atest ActivityRecordTests WindowContainerTransactionTests
Change-Id: Ie65478308d743f86bf1fd78fb5c80189801960ef