message: refactor(exhaustMap): Fix typo in ExhaustMapOperator
  Seems to be a spelling error. Class isn't exported and not used anywhere else.
diff: @@ -72,10 +72,10 @@ export function exhaustMap<T, I, R>(
  );
  }
  return (source: Observable<T>) =>
  - source.lift(new ExhauseMapOperator(project));
  + source.lift(new ExhaustMapOperator(project));
  }
  -class ExhauseMapOperator<T, R> implements Operator<T, R> {
  +class ExhaustMapOperator<T, R> implements Operator<T, R> {
  constructor(private project: (value: T, index: number) => ObservableInput<R>) {
  }
  