Fix a TODO in GN file

services/service_manager/background/tests/BUILD.gn

 # Copyright 2016 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/public/tools/bindings/mojom.gni")
 import("//services/catalog/public/tools/catalog.gni")
 import("//services/service_manager/public/cpp/service.gni")
 import("//services/service_manager/public/service_manifest.gni")
 import("//testing/test.gni")
 
 source_set("unittests") {
   testonly = true
   sources = [
     "background_service_manager_unittest.cc",
   ]
 
   deps = [
     ":test_service_interfaces",
     "//base",
     "//services/service_manager/background:lib",
-    "//services/service_manager/public/cpp:sources",
+    "//services/service_manager/public/cpp",
     "//testing/gtest",
     "//url",
   ]
 
   data_deps = [
     ":background_service_manager_test_service",
   ]
 }
 
 mojom("test_service_interfaces") {
   sources = [
     "test.mojom",
   ]
 }
 
 service("background_service_manager_test_service") {
   sources = [
     "test_service.cc",
   ]
 
   deps = [
     ":test_service_interfaces",
     "//base",
-    "//services/service_manager/public/cpp:sources",
+    "//services/service_manager/public/cpp",
     "//services/service_manager/public/interfaces",
   ]
 }
 
 service_manifest("test_manifest") {
   name = "background_service_manager_unittest"
   source = "test_manifest.json"
 }
 
 service_manifest("test_service_manifest") {
   name = "background_service_manager_test_service"
   source = "test_service_manifest.json"
 }
 
 catalog("catalog") {
   embedded_services = [ ":test_manifest" ]
 
   standalone_services = [ ":test_service_manifest" ]
 }