Stop calling #setOccluded when WM shell is enabled.

While keyguard is shown, WindowManager triggers remote animation for
KEYGUARD_(UN)OCCLUDE app transition. SysUI can know the up-to-date
keyguard occluded status throught this remote animation call, so
WindowManager doesn't need to trigger IKeygaurdService#setOccluded.

Bug: 242862775
Test: Existing tests pass.
Change-Id: I4ea4408ade39ff8558ac7627ad1994b388f1a6c6