Disable LeftoverMinimizedTasksRemover...

when back navigation flag is enabled, so users don't lose their
minimized apps in desktop.

Bug: 368317126
Test: atest DesktopTaskLimiterTest
Flag: com.android.window.flags.enable_desktop_windowing_back_navigation

Change-Id: I7de115decad387602594a21946d64e94175297a1