Remove mojom_fetcher.

mojo/public/tools/mojom_fetcher/build_gn.tmpl

-# Copyright 2015 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.
-
-## This file is automatically generated by mojo/public/tools/mojom_fetcher/mojom_gn.py.
-## Manual changes may be overwritten.
-
-import("//build/module_args/mojo.gni")
-import("$mojo_sdk_root/mojo/public/tools/bindings/mojom.gni")
-
-mojom("{{group_name}}") {
-  deps = [{% for mojom in mojoms %}
-    ":{{mojom.target_name}}",{% endfor %}
-  ]
-}
-{% for mojom in mojoms %}
-mojom("{{mojom.target_name}}") {
-  sources = [
-    "{{mojom.filename}}",
-  ]{% if mojom.import_dirs %}
-  import_dirs = [{% for dir in mojom.import_dirs %}
-    get_path_info("{{dir}}", "abspath"),{% endfor %}
-  ]{% endif %}{% if mojom.mojo_sdk_deps %}
-  mojo_sdk_deps = [{% for dep in mojom.mojo_sdk_deps %}
-    "{{dep}}",{% endfor %}
-  ]{% endif %}{% if mojom.deps %}
-  deps = [{% for dep in mojom.deps %}
-    "{{dep}}",{% endfor %}
-  ]{% endif %}
-}{% endfor %}