Investigate Atlassian IPs being blocked by Cloudflare

Previously in https://gitlab.com/gitlab-com/gl-infra/infrastructure/-/issues/6879, we had to whitelist Atlassian's IP addresses in HAProxy.

We have a recent report of a recurrence of the same problem in gitlab-org/gitlab#8185 (comment 349726346).

With the switch to Cloudflare, I suspect that Atlassian's IPs may be blocked. I checked the Workhorse logs in Kibana and I didn't see the request there.

cc @ggillies