Webhook event handling still uses old syntax

Problem/Motivation

Incoming webhooks yield errors like this:

TypeError: Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher::dispatch(): Argument #1 ($event) must be of type object, string given, called in modules/contrib/brandfolder/src/Controller/IncomingWebhookController.php

Also, the webhook event subscriber has an entity query that needs to be updated.

Steps to reproduce

Point a Brandfolder webhook at a Drupal site with the latest version of the Brandfolder module installed.

Proposed resolution

Update syntax to work with current supported Symfony/Drupal versions.

User interface changes

None

API changes

None, except webhook events will be successfully dispatched again.

Data model changes

None