Only enforce return animations when going to Launcher.

This was discussed with UX, and we came to the conclusion that
cross-task animation should use the default as it ensures a better
visual cue that the closing window is going to the background.

Bug: 323863002
Flag: com.android.systemui.shared.return_animation_framework_library
Flag: com.android.systemui.shared.return_animation_framework_long_lived
Test: manual
Change-Id: Idaa649a3eacfb0d045e4163b02312cbcffcd91d7