Edited a minor thing in part4a.md

Through the whole course, text was formal and directed to a group of people, the people write the content.

This one felt a little out of the context. I know that you, @mluukkai have done a lot to this course and I love your way of writing. I am not sure if you wrote it, but even I respect that.

If this change isn't welcomed, please don't take it personal. I am here a student willing to help, 😇

Author: Alkebsi

src/content/4/en/part4a.md

@@ -173,7 +173,7 @@ module.exports = notesRouter
 
 The module exports the router to be available for all consumers of the module.
 
-All routes are now defined for the router object, similar to what I did before with the object representing the entire application.
+All routes are now defined for the router object, similar to what was done before with the object representing the entire application.
 
 It's worth noting that the paths in the route handlers have shortened. In the previous version, we had: