Fix a typo in the changelog (#5481)

Author: ansman

CHANGES.md

@@ -1,6 +1,6 @@
 # RxJava 2 Releases #
 
-The cnagelog of version 1.x can be found at https://github.com/ReactiveX/RxJava/blob/1.x/CHANGES.md
+The changelog of version 1.x can be found at https://github.com/ReactiveX/RxJava/blob/1.x/CHANGES.md
 
 ### Version 2.1.1 - June 21, 2017 ([Maven](http://search.maven.org/#artifactdetails%7Cio.reactivex.rxjava2%7Crxjava%7C2.1.1%7C))