Removes example code that isn't correctly wired up

mash/screenlock/public/interfaces/BUILD.gn

Index: mash/screenlock/public/interfaces/BUILD.gn
diff --git a/mash/screenlock/public/interfaces/BUILD.gn b/mash/screenlock/public/interfaces/BUILD.gn
deleted file mode 100644
index b1ea7722c51476c635c9d83d7a982c2d2db49e30..0000000000000000000000000000000000000000
--- a/mash/screenlock/public/interfaces/BUILD.gn
+++ /dev/null
@@ -1,17 +0,0 @@
-# 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")
-
-group("interfaces") {
-  deps = [
-    ":constants",
-  ]
-}
-
-mojom("constants") {
-  sources = [
-    "constants.mojom",
-  ]
-}