update Todo app with gender-neutral phrasing

Projects/2-Intermediate/To-Do-App.md

@@ -2,11 +2,11 @@
 
 **Tier:** 2-Intermediate
 
-The classic To-Do application where a user can write down all the things he wants to accomplish.
+The classic To-Do application where a user can write down all the things they want to accomplish.
 
 ## User Stories
 
--   [ ] User can see an `input` field where he can type in a to-do item
+-   [ ] User can see an `input` field where they can type in a to-do item
 -   [ ] By pressing enter (or a button), the User can submit the to-do item and can see that being added to a list of to-do's
 -   [ ] User can mark a to-do as `completed`
 -   [ ] User can remove a to-do item by pressing on a button (or on the to-do item itself)