[Service Manager] Get rid of dynamic service discovery

ash/mus/BUILD.gn

Index: ash/mus/BUILD.gn
diff --git a/ash/mus/BUILD.gn b/ash/mus/BUILD.gn
index 4778732a662f5165fbd5d38467bf9704a29caddb..1a4bd7b6d968bd68ff71f6c1de9eb7ac019f8498 100644
--- a/ash/mus/BUILD.gn
+++ b/ash/mus/BUILD.gn
@@ -139,14 +139,10 @@ service("mus") {
   # TODO(beng): This target relies on //mash/session, but there is a cycle so we
   #             can't state that dependency here.
   data_deps = [
-    ":manifest",
+    ":resources",
+    ":resources_200",
     "//services/ui",
   ]
-
-  resources = [
-    "$root_out_dir/ash_mus_resources.pak",
-    "$root_out_dir/ash_mus_resources_200.pak",
-  ]
 }
 
 service_manifest("manifest") {