Remove expectation of IME StatsToken

The IME insets should always be handled by the DisplayIMEController, not
the DisplaySystemBarsController. Therefore, the
DisplaySystemBarsController will not report a IME statstoken since it is
not modifying anything related to the IME.

Bug: 380891919
Test: build
Flag: NONE cleanup
Change-Id: I422e2a57a4941d8d73fba0eebb72cad707001266