Adds grammatical determiner (#223)

src/exercise/04.js

@@ -17,7 +17,7 @@ function Board() {
   // This is the function your square click handler will call. `square` should
   // be an index. So if they click the center square, this will be `4`.
   function selectSquare(square) {
-    // 🐨 first, if there's already winner or there's already a value at the
+    // 🐨 first, if there's already a winner or there's already a value at the
     // given square index (like someone clicked a square that's already been
     // clicked), then return early so we don't make any state changes
     //