Fix typo.

collects/games/cards/cards.scrbl

@@ -6,7 +6,7 @@
 @title{Cards: Virtual Playing Cards Library}
 
 @defmodule[games/cards]{The @racketmodname[games/cards]
-module provides a toolbox for creating cards games.}
+module provides a toolbox for creating card games.}
 
 @; ----------------------------------------------------------------------
 @section{Creating Tables and Cards}