Perform the following in the Azure Console:

1. Go to Azure Active Directory
2. Go to Users and group
3. Go to User settings
4. Set Users can add gallery apps to their Access Panel to No

References:

1. https://blogs.msdn.microsoft.com/exchangedev/2014/06/05/managing-user-consent-for-applications-using-office-365-apis/
2. https://nicksnettravels.builttoroam.com/post/2017/01/24/Admin-Consent-for-Permissions-in-Azure-Active-Directory.aspx