[CentOS-mirror] Updated Whitelist IP

Dear Fabian/CentOS,

Thanks for the reply.

Our rsync source IP is 192.200.215.91 and our mirror's public IP is
23.228.76.78. May you whitelist the 192.200.215.91 instead of
23.228.76.78. We will also change our schedule to be every 4 hours
once it's whitelisted.

Thanks again