docs(descendappendrange): change subject instructions

subjects/descendappendrange/README.md

@@ -4,9 +4,9 @@
 
 - Write a function that takes an `int` max and an `int` min as parameters. The function should return a slice of `int`s with all the values between the max and min.
 
-- The `max`must be included, and `min` must be excluded.
+- The `max` must be included, and `min` must be excluded.
 
-- If `max` is inferior than or equal to `min`, return a `nil` value.
+- If `max` is inferior than or equal to `min`, return an empty slice.
 
 - `make()` is not allowed for this exercise.