Documentation: merge: one <remote> is required

merge only requires one <remote>, so "<remote>..." should be used in the
synopsis (and not "<remote> <remote>...").

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-merge.txt

@@ -10,7 +10,7 @@ SYNOPSIS
 --------
 [verse]
 'git merge' [-n] [--stat] [--no-commit] [--squash] [-s <strategy>]...
-	[-m <msg>] <remote> <remote>...
+	[-m <msg>] <remote>...
 'git merge' <msg> HEAD <remote>...
 
 DESCRIPTION