urlrequest: fix documentation on body/headers

Author: tito

kivy/network/urlrequest.py

@@ -48,8 +48,8 @@ def bug_posted(req, result):
         '@action': 'show'})
     headers = {'Content-type': 'application/x-www-form-urlencoded',
               'Accept': 'text/plain'}
-    req = UrlRequest('bugs.python.org', on_success=bug_posted, body=params,
-            headers=headers)
+    req = UrlRequest('bugs.python.org', on_success=bug_posted, req_body=params,
+            req_headers=headers)
 
 
 '''