fix distinct factory for operator call syntax
fix distinct factory for operator call syntax

ReactiveX/RxCpp,alexeymarkov/RxCpp,Reactive-Extensions/RxCpp,Reactive-Extensions/RxCpp,Reactive-Extensions/RxCpp,alexeymarkov/RxCpp,ReactiveX/RxCpp,alexeymarkov/RxCpp,ReactiveX/RxCpp