I am not sure about their hosted option. Normally you can upgrade any plugin by navigating to the URL /admin/upgrade. Else you should contact them.
Also I realized since the error message is already added in your case the above solution may not work for you. So I recommend you to run the below command in your console.
cd /var/discourse
rails c
AdminDashboardData.clear_problem_message(Patreon::Api::ACCESS_TOKEN_INVALID)