Documentation: add missing :: in config.txt

bed575e (commit: support commit.status, --status, and --no-status,
2009-12-07) forgot to add the :: that sets off an item from the
paragraph that explains it, breaking the layout.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: trast

Documentation/config.txt

@@ -716,7 +716,7 @@ color.ui::
 	terminal. When more specific variables of color.* are set, they always
 	take precedence over this setting. Defaults to false.
 
-commit.status
+commit.status::
 	A boolean to enable/disable inclusion of status information in the
 	commit message template when using an editor to prepare the commit
 	message.  Defaults to true.