docs(required-named-parameters): correct grammar

subjects/mobile-dev/named-required-sum/README.md

@@ -2,6 +2,7 @@
 
 ### Instructions
 
-Write a function called `namedRequiredSum()` that accepts _required_ named parameters `first`, `second`, `third` and returns their sum. All the parameters are integers.
-
-- Note: Find out how to make required [named parameters](https://dart.dev/guides/language/language-tour).
+Write a function named `namedRequiredSum`, that returns the sum of its required [named](https://dart.dev/guides/language/language-tour) `int` parameters:
+- `first`
+- `second`
+- `third`