1.x: fix renamed operator in Single.
1.x: fix renamed operator in Single.

There was a cross dependency between two PRs yielding a broken
compilation in main.
simonbasle/RxJava,nurkiewicz/RxJava,tilal6991/RxJava,davidmoten/RxJava,hzysoft/RxJava,simonbasle/RxJava,simonbasle/RxJava,jacek-rzrz/RxJava,weikipeng/RxJava,jacek-rzrz/RxJava,klemzy/RxJava,tilal6991/RxJava,nurkiewicz/RxJava,nurkiewicz/RxJava,davidmoten/RxJava,hzysoft/RxJava,tilal6991/RxJava,weikipeng/RxJava,hzysoft/RxJava,stevegury/RxJava,klemzy/RxJava,stevegury/RxJava,jacek-rzrz/RxJava,stevegury/RxJava,hyleung/RxJava,zsxwing/RxJava,weikipeng/RxJava,davidmoten/RxJava,klemzy/RxJava,hyleung/RxJava,zsxwing/RxJava,hyleung/RxJava,zsxwing/RxJava