docs(operator-creation): fix typo (#5057)
docs(operator-creation): fix typo (#5057)

Remove apostrophe from possessive "its" in operator-creation.md
ReactiveX/rxjs,ReactiveX/rxjs,trxcllnt/RxJS,kwonoj/RxJS,benlesh/RxJS,martinsik/rxjs,ReactiveX/rxjs,kwonoj/RxJS,benlesh/RxJS,trxcllnt/RxJS,kwonoj/RxJS,trxcllnt/RxJS,ReactiveX/RxJS,ReactiveX/rxjs,trxcllnt/RxJS,ReactiveX/RxJS,ReactiveX/RxJS,martinsik/rxjs,kwonoj/RxJS,martinsik/rxjs,benlesh/RxJS,benlesh/RxJS,martinsik/rxjs,ReactiveX/RxJS