[infra_ui] Remove deprecated files

app_flowy/packages/flowy_infra_ui/platform_interface/keyboard_web/lib/keyboard_web.dart

@@ -1,16 +0,0 @@
-library keyboard_web;
-
-import 'package:flutter_web_plugins/flutter_web_plugins.dart';
-import 'package:keyboard_platform_interface/keyboard_platform_interface.dart';
-
-class KeyboardPlugin extends KeyboardPlatform {
-  static void registerWith(Registrar registrar) {
-    KeyboardPlatform.instance = KeyboardPlugin();
-  }
-
-  @override
-  Stream<bool> get onKeyboardChange async* {
-    // suppose that keyboard won't show in web side
-    yield false;
-  }
-}