[Mailer][Brevo] Remove tags from mandatory event arguments

'tags' in not mandatory part of an event
therefore it got removed from the validation process

src/Symfony/Component/Mailer/Bridge/Brevo/Webhook/BrevoRequestParser.php

@@ -49,7 +49,6 @@ protected function doParse(Request $request, #[\SensitiveParameter] string $secr
             || !isset($content['email'])
             || !isset($content['message-id'])
             || !isset($content['ts_event'])
-            || !isset($content['tags'])
         ) {
             throw new RejectWebhookException(406, 'Payload is malformed.');
         }