WindowManagerService: remove unused support for onlyCore mode

The "core apps only" mode of system_server is no longer used, and
onlyCore is hard-coded to false.  For details, see http://ag/17685636.

Remove the corresponding obsolete code from WindowManagerService.

Bug: 208476087
Change-Id: Icec64be737709b63c14f0d2a73c9abf6894ce87e

services/java/com/android/server/SystemServer.java

@@ -1565,8 +1565,7 @@ public final class SystemServer implements Dumpable {
             // WMS needs sensor service ready
             mSystemServiceManager.startBootPhase(t, SystemService.PHASE_WAIT_FOR_SENSOR_SERVICE);
             wm = WindowManagerService.main(context, inputManager, !mFirstBoot,
-                    /* onlyCore= */ false, new PhoneWindowManager(),
-                    mActivityManagerService.mActivityTaskManager);
+                    new PhoneWindowManager(), mActivityManagerService.mActivityTaskManager);
             ServiceManager.addService(Context.WINDOW_SERVICE, wm, /* allowIsolated= */ false,
                     DUMP_FLAG_PRIORITY_CRITICAL | DUMP_FLAG_PROTO);
             ServiceManager.addService(Context.INPUT_SERVICE, inputManager,