[rancid] How do I make Rancid forget about a switch?

[Chris Knight]

Yesterday I pulled two switches and an ASA from my network.  As
expected, at a certain point I started getting notifications that
Rancid was unable to pull the configs after X hours. So, I commented
out the switches and asa from routers.db, but I am still getting
alerts.  Yes, I know I could google it, but I've been up for 36 hours
and I'm hoping someone will show some compassion and tell me the quick
fix.  :)

-Chris