ghcr.io/zulip/zulip-server:11.5-0

This is the first release of the new ghcr.io/zulip/zulip-server; it contains Zulip Server 11.5.

docker pull ghcr.io/zulip/zulip-server:11.5-0

See the upgrade documentation for upgrade steps from zulip/docker-zulip.