SWSoft decided that the wise thing to do is to start advertising their products in the control panel, effectively spamming the clients that pay a lot of money for the licenses.
To disable the promo, edit the language file, located here:
/usr/local/psa/admin/plib/locales/en-US/messages_en-US.php
Search for the following string:
virtuozzo__promotion or virtuozzo__promotion_top
SWSoft promised that it will remove the advertising from future versions. Let’s hope they do.
Remember, you may need to edit different files for different languages.
Edit: This also works in versions 8.1.1, 8.2.0 and 8.2.1