lualoader: use more concise verbiage for autoboot

The behavior remains the same, but lualoader now uses the more concise
verbiage that forthloader used.  This is particularly important because
the previous line would exceed the right boundary of the menu and run
straight into space that would typically be allowed for the logo.

This makes it slightly easier to port logos from forthloader to
lualoader.

stand/lua/menu.lua

@@ -522,8 +522,7 @@ function menu.autoboot(delay)
 			last = time
 			screen.setcursor(x, y)
 			print("Autoboot in " .. time ..
-			    " seconds, hit [Enter] to boot" ..
-			    " or any other key to stop     ")
+			    " seconds. [Space] to pause")
 			screen.defcursor()
 		end
 		if io.ischar() then