small changes in dmenu.1

dmenu.1

@@ -7,7 +7,7 @@ dmenu \- dynamic menu
 .SH DESCRIPTION
 .SS Overview
 .B dmenu
-is a generic, highly customizable, and efficient menu for the X Window System,
+is a generic, highly customizable, and efficient menu for X,
 originally designed for
 .BR dwm (1).
 It supports arbitrary, user defined menu contents.