docs(README.md): fix example (#115)

Author: Antoine Lelaisant

README.md

@@ -248,7 +248,7 @@ const NewMessagesIndicator = () => {
   };
 
   if (error) {
-    return <div>Error! {error.message}`</div>;
+    return <div>Error! {error.message}</div>;
   };
 
   return <div>{data.newMessagesCount} new messages</div>;