monitoring: fix alert banner wording, link to grafana
Created by: bobheadxi
for https://github.com/sourcegraph/sourcegraph/issues/12026
- remove "are" from message so that the message is okay for all pluralities ("1 alert across 1 service currently firing", "12 alerts across 4 services currently firing")
- trigger a
window.location
reload on/-/debug/*
paths so that the link in the alert to grafana works (thread)