update dynamic-css typo

users can only see two boxes (the id box and the password box), not three.

Projects/1-Beginner/Dynamic-CSSVar-app.md

@@ -17,7 +17,7 @@ changing them from within the app.
 
 ## User Stories
 
--   [ ] User can see three two boxes to be used to enter a User ID and Password
+-   [ ] User can see two boxes to be used to enter a User ID and Password
 along with 'Cancel' and 'Login' buttons underneath them. The default background
 color of the text boxes is white.
 -   [ ] User can enter a user id and password into the text boxes.