core: fixed typo of year in README

- reported by Anthony Messina

README

@@ -90,7 +90,7 @@ Kamailio.org and SIP Express Router (SER) from iptel.org.
 
 Kamailio is the result of a merge of the code base and years of experience from
 both developer teams. During the development of the release 4.0, autumn-winter
-of 201w, the merger of the products was completed and a unified product was
+of 2012, the merger of the products was completed and a unified product was
 released.
 
 See http://www.kamailio.org/ for the story of SER, OpenSER and Kamailio.