Fix Renewal Emails to Not Come from paul@gtilab.com

Renewal emails are currently sent from an email address "paul@gtilab.com" - notice GTI not GIT.

First, this domain is not ours and could cause people concern/get the email flagged as spam. Second, we should send from a more generic address - users don't know who Paul is.

We should send these emails from renewals@gitlab.com.