Navigate to "admin.microsoft.com" and click "Active Users"

Click "..."\
Select "filters" and click "Global Admins"

You are now presented with a list of accounts that have the global admin role. Identify any accounts that are normal users accounts (these typically have an Office license of some description)

Click "Manage roles" and then select "User (no admin center access)".

You have now successfully removed admin roles from this standard user account. Meaning in the event of this account being breached the damage caused will be much less!

Remove Admin Access for User in Microsoft Admin Center