message: refactor: fix up the name, remove the 2
diff: @@ -127,7 +127,7 @@ export function groupBy<T, K, R>(
  lift(source, function (this: Subscriber<GroupedObservable<K, R>>, source: Observable<T>) {
  const subscriber = this;
  const groups = new Map<K, Subject<any>>();
  - let groupBySubscriber: GroupBySubscriber2<any>;
  + let groupBySubscriber: GroupBySubscriber<any>;
  function createGroupedObservable<K, T>(key: K, groupSubject: Subject<any>) {
  const result: any = new Observable<T>((goSubscriber) => {
  @@ -144,7 +144,7 @@ export function groupBy<T, K, R>(
  return result;
  }
  - groupBySubscriber = new GroupBySubscriber2(
  + groupBySubscriber = new GroupBySubscriber(
  subscriber,
  (value: T) => {
  let key: K;
  @@ -226,7 +226,7 @@ export interface RefCountSubscription {
  attemptedToUnsubscribe: boolean;
  }
  -class GroupBySubscriber2<T> extends Subscriber<T> {
  +class GroupBySubscriber<T> extends Subscriber<T> {
  count = 0;
  unsubAttempted = false;
  