Documentation: format-patch has no --mbox option

git-applymbox and git-mailinfo refer to a --mbox option of
git-format-patch when talking about their -k options. But there
is no such option.  What -k does to the former two commands is
to keep the Subject: lines unmunged, meant to be used on output
generated with format-patch -k.

Signed-off-by: Frank Lichtenheld <frank@lichtenheld.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/git-applymbox.txt

@@ -31,7 +31,7 @@ OPTIONS
 	whitespaces, (3) '[' up to ']', typically '[PATCH]', and
 	then prepends "[PATCH] ".  This flag forbids this
 	munging, and is most useful when used to read back 'git
-	format-patch --mbox' output.
+	format-patch -k' output.
 
 -m::
 	Patches are applied with `git-apply` command, and unless

Documentation/git-mailinfo.txt

@@ -30,7 +30,7 @@ OPTIONS
 	whitespaces, (3) '[' up to ']', typically '[PATCH]', and
 	then prepends "[PATCH] ".  This flag forbids this
 	munging, and is most useful when used to read back 'git
-	format-patch --mbox' output.
+	format-patch -k' output.
 
 -u::
 	The commit log message, author name and author email are