ls-remote: document --quiet option

cefb2a5 ("ls-remote: print URL when no repo is specified") added a
quiet option to ls-remote, but didn't add it to the documentation.  Add
it.

Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-ls-remote.txt

@@ -10,7 +10,7 @@ SYNOPSIS
 --------
 [verse]
 'git ls-remote' [--heads] [--tags]  [--upload-pack=<exec>]
-	      [--exit-code] <repository> [<refs>...]
+	      [-q | --quiet] [--exit-code] <repository> [<refs>...]
 
 DESCRIPTION
 -----------
@@ -29,6 +29,10 @@ OPTIONS
 	both, references stored in refs/heads and refs/tags are
 	displayed.
 
+-q::
+--quiet::
+	Do not print remote URL to stderr.
+
 --upload-pack=<exec>::
 	Specify the full path of 'git-upload-pack' on the remote
 	host. This allows listing references from repositories accessed via