[Code cleanup]Remove webui keyboard mojo binding

ui/keyboard/webui/keyboard.mojom

Index: ui/keyboard/webui/keyboard.mojom
diff --git a/ui/keyboard/webui/keyboard.mojom b/ui/keyboard/webui/keyboard.mojom
deleted file mode 100644
index 889f75c3095e80132220013644111a1735dcada3..0000000000000000000000000000000000000000
--- a/ui/keyboard/webui/keyboard.mojom
+++ /dev/null
@@ -1,21 +0,0 @@
-// 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.
-
-module keyboard;
-
-interface KeyboardUIHandlerMojo {
-  SetTextInputTypeObserver(TextInputTypeObserver observer);
-
-  SendKeyEvent(string? event_type,
-               int32 char_value,
-               int32 key_code,
-               string? key_name,
-               int32 modifiers);
-
-  HideKeyboard();
-};
-
-interface TextInputTypeObserver {
-  OnTextInputTypeChanged(string? input_type);
-};