donate: change alerting thresholds for card testing

We have had a couple incidents recently where we had card testing but those alerts never fired.

I believe the thresholds were not set correctly. First, they were kind of too tolerant, but also, the for mixed with a rate() query meant that we never had the sustained load to trigger the alert.

So, instead, we sample over a longer period (one hour) and remove the for threshold entirely. We also check all transactions, because we have a pretty good measure of what a "normal" is nowadays.