[TASK] Avoid implicitly nullable class method parameter in `EXT:webhooks`

With PHP 8.4 marking method parameter implicitly nullable
is deprecated and will emit a `E_DEPRECATED` warning. One
recommended way to resolve this, is making it explicitly
nullable using the `?` nullable operator. [1]

This prepares the way towards PHP 8.4 compatibility.

[1] https://php.watch/versions/8.4/implicitly-marking-parameter-type-nullable-deprecated

Resolves: #104187
Releases: main, 12.4
Change-Id: I80b1494413016658e6c5ed88485cce887178fdbf
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/84874


Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Garvin Hicking <gh@faktor-e.de>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Garvin Hicking <gh@faktor-e.de>

typo3/sysext/webhooks/Classes/Factory/WebhookInstructionFactory.php

@@ -46,11 +46,11 @@ class WebhookInstructionFactory
         string $method = 'POST',
         bool $verifySSL = true,
         array $additionalHeaders = [],
-        string $name = null,
-        string $description = null,
-        WebhookType $webhookType = null,
-        string $identifier = null,
-        int $uid = null,
+        ?string $name = null,
+        ?string $description = null,
+        ?WebhookType $webhookType = null,
+        ?string $identifier = null,
+        ?int $uid = null,
     ): WebhookInstruction {
         return new WebhookInstruction(
             $url,