Replace Drupal 8 Logo with Drupal 9 branding

admin Toolbar is an example Module for the user Guide Proejct. Because D9 will be released soon modules/contrib/admin_toolbar/admin_toolbar_tools/misc/icons/ffffff/d8-item.svg should be replaced with the svg from https://www.drupal.org/about/media-kit/logos

Not sure if an if statement detecting the drupal version used is neccecary to server both images depending on drupal core version.