Fix small typo in 02.md (#41)

Turn `it's` -> `its`

Author: emzoumpo

src/exercise/02.md

@@ -25,7 +25,7 @@ Production deploys:
 - [Final](https://react-hooks.netlify.app/isolated/final/02.js)
 
 In this exercise, we're going to enhance our `<Greeting />` component to get
-it's initial state value from localStorage (if available) and keep localStorage
+its initial state value from localStorage (if available) and keep localStorage
 updated as the `name` is updated.
 
 ## Extra Credit