Update job name to be more general

The job name should really be the same for all metrics published by this
_thing_. We currently have publisher (for the web app) and
publisher-worker for the worker. I think publisher-metrics is probably a
good job name for these specificly metricsy things.

script/mail_fetcher

@@ -56,6 +56,6 @@ end
 
 Rails.logger.info "Finished running MailFetcher in #{Rails.env} mode - #{Time.zone.now.utc}"
 Prometheus::Client::Push.new(
-  job: "publisher_fact_check_emails",
+  job: "publisher-metrics",
   gateway: ENV.fetch("PROMETHEUS_PUSHGATEWAY_URL"),
 ).add(registry)