Fix truncation usage for RequestException (#10912)

This show a working example on how to setup truncation in `bootstrap/app.php` as the previous code usage doesn't work on web request. 

> `ApplicationBuilder::withExceptions($using)` method only resolves the `$using` callback after resolving `Illuminate\Foundation\Exceptions\Handler`. Therefore, any value set via `new RequestException($response)` will only consist of resolved  `prepareMessage()` value before `Handler`.

Author: crynobone

http-client.md

@@ -397,17 +397,17 @@ return Http::post(/* ... */)->throw(function (Response $response, RequestExcepti
 })->json();
 ```
 
-By default, `RequestException` messages are truncated to 120 characters when logged or reported. To customize or disable this behavior, you may utilize the `truncateRequestExceptionsAt` and `dontTruncateRequestExceptions` methods when configuring your application's exception handling behavior in your `bootstrap/app.php` file:
+By default, `RequestException` messages are truncated to 120 characters when logged or reported. To customize or disable this behavior, you may utilize the `truncateAt` and `dontTruncate` methods when configuring your application's registered behavior in your `bootstrap/app.php` file:
 
 ```php
-use Illuminate\Foundation\Configuration\Exceptions;
+use Illuminate\Http\Client\RequestException;
 
-->withExceptions(function (Exceptions $exceptions): void {
+->registered(function (): void {
     // Truncate request exception messages to 240 characters...
-    $exceptions->truncateRequestExceptionsAt(240);
+    RequestException::truncateAt(240);
 
     // Disable request exception message truncation...
-    $exceptions->dontTruncateRequestExceptions();
+    RequestException::dontTruncate();
 })
 ```