[Решено] Development site banner displaying on production website

Background of the issue:
I am trying to deploy my staging site to production, but I encounter an issue with a banner appearing. My production site is: скрытая ссылка. I use WPEngine for hosting, make changes to a staging environment, and then push that environment to production when tested.

Symptoms:
An error banner appears at the bottom of my site: "This site is registered on wpml.org as a development site. Switch to a production site key to remove this banner."

Questions:
How can I get rid of this banner?
How can I make sure that when I deploy staging to production, that this banner doesn't appear again?