Documentation: git push repository can also be a remote

This is copied from pull-fetch-param.txt and helps the reader
to not get stuck in the URL section.

Signed-off-by: Anders Melchiorsen <mail@cup.kalibalik.dk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-push.txt

@@ -28,7 +28,9 @@ OPTIONS
 -------
 <repository>::
 	The "remote" repository that is destination of a push
-	operation.  See the section <<URLS,GIT URLS>> below.
+	operation.  This parameter can be either a URL
+	(see the section <<URLS,GIT URLS>> below) or the name
+	of a remote (see the section <<REMOTES,REMOTES>> below).
 
 <refspec>...::
 	The canonical format of a <refspec> parameter is