Remove ActivityRecord mDeferHidingClient since shell transition enabled

To prevent the client visibility change during/before transition
animation.

Flag: com.android.window.flags.remove_defer_hiding_client
Bug: 382485959
Test: Verify the surface view won't be release during animation while
closing pip-able app.

Change-Id: I5ff020d73d09352713a029d5f95d2b27e8b32148