Rely on SystemService#onSwitchUser() in IMMS.

SystemService class has already provided SystemService#onSwitchUser()
callback event.  We do not need to set up SynchronousUserSwitchObserver
separately in InputMethodManagerService.

Bug: 25816558
Bug: 26279466
Change-Id: I8ce2ba1335ae4caa35f9a21d87b751bfb4614033
1 file changed