Update default admin group for Ubuntu.

Author: geerlingguy

examples/prod/bootstrap/example.vars.yml

@@ -1,8 +1,8 @@
 ---
 admin_user: my_admin_username
 
-# On RHEL/CentOS, 'wheel'; on Debian/Ubuntu, 'root'.
-admin_group: root
+# On RHEL/CentOS, 'wheel'; on Debian/Ubuntu, 'sudo'.
+admin_group: sudo
 
 # IMPORTANT: Configure your own password for the admin user account. To generate
 # a password hash, use either of the following commands: