Mojo C++ bindings: remove some usage of AssociatedGroup from user code.

services/ui/ws/window_server.cc

Index: services/ui/ws/window_server.cc
diff --git a/services/ui/ws/window_server.cc b/services/ui/ws/window_server.cc
index b96c0c980bfa84166c6d683e15e5b7bfb4c3f429..7dfcf12dce0a4b7336ab12a62bcb7541bb8f9e21 100644
--- a/services/ui/ws/window_server.cc
+++ b/services/ui/ws/window_server.cc
@@ -533,10 +533,6 @@ cc::mojom::DisplayCompositor* WindowServer::GetDisplayCompositor() {
   return display_compositor_.get();
 }
 
-mojo::AssociatedGroup* WindowServer::GetDisplayCompositorAssociatedGroup() {
-  return display_compositor_.associated_group();
-}
-
 bool WindowServer::GetFrameDecorationsForUser(
     const UserId& user_id,
     mojom::FrameDecorationValuesPtr* values) {