docs: fix error on complex example (#560)

Catch already sets error to error.message. So in render it should just show state.error.

Author: tteke

README.md

@@ -248,7 +248,7 @@ function Login() {
         </div>
         <button type="submit">Submit{state.loading ? '...' : null}</button>
       </form>
-      {state.error ? <div role="alert">{state.error.message}</div> : null}
+      {state.error ? <div role="alert">{state.error}</div> : null}
       {state.resolved ? (
         <div role="alert">Congrats! You're signed in!</div>
       ) : null}