Documentation/git-submodule: typofix

Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Documentation/git-submodule.txt

@@ -70,7 +70,7 @@ OPTIONS
 -n, --summary-limit::
 	This option is only valid for the summary command.
 	Limit the summary size (number of commits shown in total).
-	Giving 0 will disable the summary; a negative number means unlimted
+	Giving 0 will disable the summary; a negative number means unlimited
 	(the default). This limit only applies to modified submodules. The
 	size is always limited to 1 for added/deleted/typechanged submodules.