amend javadocs for Observable.subscribe() as per #3523
amend javadocs for Observable.subscribe() as per #3523

klemzy/RxJava,simonbasle/RxJava,davidmoten/RxJava,hyleung/RxJava,stevegury/RxJava,stevegury/RxJava,davidmoten/RxJava,simonbasle/RxJava,tilal6991/RxJava,nurkiewicz/RxJava,zsxwing/RxJava,jacek-rzrz/RxJava,klemzy/RxJava,hyleung/RxJava,davidmoten/RxJava,zsxwing/RxJava,nurkiewicz/RxJava,nurkiewicz/RxJava,weikipeng/RxJava,jacek-rzrz/RxJava,stevegury/RxJava,hyleung/RxJava,tilal6991/RxJava,weikipeng/RxJava,zsxwing/RxJava,simonbasle/RxJava,tilal6991/RxJava,hzysoft/RxJava,jacek-rzrz/RxJava,hzysoft/RxJava,klemzy/RxJava,weikipeng/RxJava,hzysoft/RxJava