message: Remove unused prop from ThemeWatcher
diff: @@ -24,9 +24,6 @@ import { ActionPayload } from '../../dispatcher/payloads';
  import { SettingLevel } from "../SettingLevel";
  export default class ThemeWatcher {
  - // XXX: I think this is unused.
  - static _instance = null;
  -
  private themeWatchRef: string;
  private systemThemeWatchRef: string;
  private dispatcherRef: string;
  