Send alert only once per hour for relays passing the nickname/contact info/flag thresholds

Right now those alerts do not have any for clause included which, if I understand the docs at https://prometheus.io/docs/prometheus/latest/configuration/alerting_rules/ correctly, triggers an alert in case the condition matches on any update. Having the alerts in question trigger a notification only once per hour seems to be the right thing to do given that we only get Onionoo updates once per hour anyway.