docs(check_user_name): fix typo

subjects/check_user_name/README.md

@@ -17,7 +17,7 @@ You will also have to create a `User` struct which has:
   - `new`: which initializes the struct.
   - `send_name`: which takes only `self` as argument and returns an `Option<&str>` with `None` if the user is a guest or the `name` if the `AccessLevel` has any of the other options.
 - Other functions:
-  - `check_user_name`: which takes a `User`, calls `send_name` and returns a `tuple` with `true` and the user `name` if `send_name` returns the name or `false` and `"Error: User is guest"` if not
+  - `check_user_name`: which takes a `User`, calls `send_name` and returns a `tuple` with `true` and the user `name` if `send_name` returns the name or `false` and `"Error: User is guest"` if not.
 
 ### Expected Functions and Data Structures