In order to be eligible to remove the © OpenStreetMap attribution, you have to switch the map source from MapTiler Planet to MapTiler Planet Lite, which doesn't contain data protected by the OpenStreetMap license.
Change the map source to Planet Lite
In MapTiler Cloud, select a map you want to use, and click on the Customize a copy button.
In the Customize tool, go to the Misc tab and change the Data source from MapTiler Planet (default) to MapTiler Planet Lite.
Click on the Save button, name your map, click on the Create button, click on the Publish button, and now you can start using your map without the © OpenStreetMap attribution in videos, print, on the web, or in games. The © MapTiler attribution must be still present!
How to get a copyright-free map without the MapTiler attribution
To be eligible to remove the © MapTiler attribution, you need to contact MapTiler to get permission.