grafana: Enable auto-sign-up.
grafana: Enable auto-sign-up.

This avoids the need to explicitly create new users in Grafana, by
simply trusting Teleport.

andersk/zulip,rht/zulip,zulip/zulip,zulip/zulip,rht/zulip,rht/zulip,rht/zulip,zulip/zulip,zulip/zulip,rht/zulip,andersk/zulip,zulip/zulip,zulip/zulip,andersk/zulip,andersk/zulip,andersk/zulip,rht/zulip,rht/zulip,zulip/zulip,andersk/zulip,andersk/zulip