fix: typo in challenge solution (#7816)

Author: aalhoura

src/content/learn/removing-effect-dependencies.md

@@ -1241,7 +1241,7 @@ export default function Timer() {
 
 </Sandpack>
 
-Instead of reading `count` inside the Effect, you pass a `c => c + 1` instruction ("increment this number!") to React. React will apply it on the next render. And since you don't need to read the value of `count` inside your Effect anymore, so you can keep your Effect's dependencies empty (`[]`). This prevents your Effect from re-creating the interval on every tick.
+Instead of reading `count` inside the Effect, you pass a `c => c + 1` instruction ("increment this number!") to React. React will apply it on the next render. And since you don't need to read the value of `count` inside your Effect anymore, you can keep your Effect's dependencies empty (`[]`). This prevents your Effect from re-creating the interval on every tick.
 
 </Solution>