Fix typo in validation docs

Author: waypar

content/docs/validation.mdx

@@ -68,7 +68,7 @@ and a `message` string which will be used to display the error in the form.
 ```js
 const AdditionalErrorsExample = () => {
 
-  const [additionalErrors, setAdditionalErrors] = useState<ErrorObject[])([]);
+  const [additionalErrors, setAdditionalErrors] = useState<ErrorObject[]>([]);
 
   const addAdditionalError = () => {
       const newError: ErrorObject = {