GN: Replace mojo/system.gni with forwarding groups

mojo/services/public/cpp/geometry/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import("//mojo/system.gni")
-
 # GYP version: mojo/mojo_services.gypi:mojo_geometry_lib
 component("geometry") {
   output_name = "mojo_geometry_lib"
 
   deps = [
     "//skia",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//mojo/environment:chromium",
+    "//mojo/public/c/system:for_component",
     "//mojo/services/public/interfaces/geometry",
-  ] + mojo_system_for_component
+  ]
 
   forward_dependent_configs_from = [ "//ui/gfx" ]
 
   defines = [
     "MOJO_GEOMETRY_IMPLEMENTATION",
   ]
 
   sources = [
     "lib/geometry_type_converters.cc",
     "geometry_type_converters.h",
     "mojo_geometry_export.h",
   ]
 }