doc/memos: Fix link

Author: LasseRosenow

doc/memos/rdm0000.md

@@ -143,7 +143,7 @@ Matthias Wählisch for their comments and suggestions.
 ## References
 
 - Internet Engineering Task Force ([IETF](http://ietf.org/))
-- Guide to [Contributing to RIOT](https://github.com/RIOT-OS/RIOT/wiki/Contributing-to-RIOT)
+- Guide to [Contributing to RIOT](https://github.com/RIOT-OS/RIOT/blob/master/CONTRIBUTING.md)
 
 ## Revision