Fix doc typo (#4678)

Fix a typo in the `requireValue` example

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  ## Unreleased fix/major/minor

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<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Documentation**
* Corrected AsyncValue documentation examples to reference the accurate
API method, ensuring consistent and correct guidance for developers
implementing asynchronous functionality.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Remi Rousselet <darky12s@gmail.com>

Author: rxlabz

packages/riverpod/lib/src/core/async_value.dart

@@ -407,8 +407,8 @@ class AsyncValueIsLoadingException implements Exception {
 ///
 /// ```dart
 /// Widget build(BuildContext context, WidgetRef ref) {
-///   // Reading .requiredValue will be throw both on loading and error states.
-///   final User user = ref.watch(userProvider).requiredValue;
+///   // Reading .requireValue will be thrown both on loading and error states.
+///   final User user = ref.watch(userProvider).requireValue;
 ///
 ///   ...
 /// }