docs(shoppinglistsort): fix instructions

subjects/shoppinglistsort/README.md

@@ -4,7 +4,7 @@
 
 You were sent to the supermarket with a shopping list. To make your shopping faster, write a function `ShoppingListSort()` that takes a slice of strings and sorts it, according to the string length, returning a slice in which the strings appear in ascending order.
 
-- The length of the strings cannot repeat itself.
+- Strings within the input slice must be of different lengths.
 
 ### Expected function