fix another snippets ignore

Author: saihaj

src/pages/learn/schema.mdx

@@ -242,7 +242,7 @@ myField: ["a", null, "b"] // valid
 
 Lastly, you can also have a Non-Null List of Non-Null `String` types:
 
-<!-- snippet-ignore -->
+{/* <!-- snippet-ignore --> */}
 ```graphql
 myField: [String!]!
 ```