tweak HTTP status code language

Author: dret

versions/3.0.md

@@ -47,8 +47,7 @@ Some examples of possible media type definitions:
   application/vnd.github.v3.patch
 ```
 ##### <a name="httpCodes"></a>HTTP Status Codes
-The HTTP Status Codes are used to indicate the status of the executed operation.
-The available status codes are described by [RFC 7231](http://tools.ietf.org/html/rfc7231#section-6) and in the [IANA Status Code Registry](http://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml).
+The HTTP Status Codes are used to indicate the status of the executed operation. The available status codes are initially defined by [RFC 7231](http://tools.ietf.org/html/rfc7231#section-6) and registered status codes are listed in the [IANA Status Code Registry](http://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml).
 
 ## Specification