Decommission the snowflake-reg-test.appspot.com reflector

snowflake-reg-test.appspot.com is a frontend for snowflake-broker.bamsoftware.com, briefly used with a Google domain front. It never actually worked, because this was around the time that Google stopped domain fronting.

2018-04-15 Change to standalone broker.
2018-04-30 Switch to an Azure domain front.

On 2020-02-05, arlolra and I got an email saying that we needed to upgrade the deployment to the Go 1.11 runtime by 2020-05-01. I tried doing that today, but got the error

ERROR: (gcloud.app.deploy) Error Response: [7] Access Not Configured.
Cloud Build has not been used in project snowflake-reg-test before or
it is disabled. Enable it by visiting
https://console.developers.google.com/apis/api/cloudbuild.googleapis.com/overview?project=snowflake-reg-test
then retry. If you enabled this API recently, wait a few minutes for the
action to propagate to our systems and retry.

I tried doing that, but apparently there is no truly free tier anymore and you can't deploy or redeploy apps without setting up a billing account. Rather than go through with that, I propose that we just disable the unused service.