docs: change hardcoded name to field name

Author: LeCarbonator

examples/react/next-server-actions/src/app/client-component.tsx

@@ -37,7 +37,7 @@ export const ClientComp = () => {
           return (
             <div>
               <input
-                name="age" // must explicitly set the name attribute for the POST request
+                name={field.name} // must explicitly set the name attribute for the POST request
                 type="number"
                 value={field.state.value}
                 onChange={(e) => field.handleChange(e.target.valueAsNumber)}