refactor(mergeAll): fix typings
refactor(mergeAll): fix typings

benlesh/RxJS,benlesh/RxJS,martinsik/rxjs,martinsik/rxjs,ReactiveX/RxJS,benlesh/RxJS,ReactiveX/RxJS,ReactiveX/rxjs,martinsik/rxjs,ReactiveX/RxJS,ReactiveX/RxJS,ReactiveX/rxjs,ReactiveX/rxjs,martinsik/rxjs,benlesh/RxJS,ReactiveX/rxjs