Update GN build files for new prefs location.

components/pref_registry/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.
 
 source_set("pref_registry") {
   sources = [
     "pref_registry_syncable.cc",
     "pref_registry_syncable.h",
   ]
 
   deps = [
     "//base",
-    "//base:prefs",
     "//base/third_party/dynamic_annotations",
+    "//components/prefs",
   ]
 }
 
 source_set("test_support") {
   testonly = true
   sources = [
     "testing_pref_service_syncable.cc",
     "testing_pref_service_syncable.h",
   ]
 
   public_deps = [
     ":pref_registry",
   ]
 
   deps = [
     "//base",
-    "//base:prefs",
-    "//base:prefs_test_support",
+    "//components/prefs:test_support",
   ]
 }