[RxJava2.x][wiki] no fromEmitter() operator

[CoXier]

Hi, there is no fromEmitter() operator in RxJava1.x and RxJava 2.x now. Should you update wiki?

https://github.com/ReactiveX/RxJava/wiki/Creating-Observables

[akarnokd]

Should

This is an open-source project. If you find incorrect or missing stuff, you are welcome to post a PR.
The wiki can be PR'd too: https://github.com/ReactiveX/RxJava/tree/2.x/docs

[CoXier]

I just remove this line in #6128