Fix typo in Removing from an array part (#4171)

beta/src/pages/learn/updating-arrays-in-state.md

@@ -208,7 +208,7 @@ setArtists(
 );
 ```
 
-Here, `artists.filter(s => s.id !== artist.id)` means "create an array that consists of those `artists` whose IDs are different from `artist.id`." In other words, each artist's "Delete" button will filter _that_ artist out of the array, and then request a re-render with the resulting array. Note that `filter` does not modify the original array.
+Here, `artists.filter(a => a.id !== artist.id)` means "create an array that consists of those `artists` whose IDs are different from `artist.id`." In other words, each artist's "Delete" button will filter _that_ artist out of the array, and then request a re-render with the resulting array. Note that `filter` does not modify the original array.
 
 ### Transforming an array {/*transforming-an-array*/}
 
@@ -1972,4 +1972,4 @@ With Immer, you can pick the style that feels the most natural for each separate
 
 </Solution>
 
-</Challenges>
+</Challenges>