Hermit channels don't seem to update reliably

[alecthomas]

After creating the go@tip channel, Hermit updated it once on Dec 2 but has not updated it since, even though there are more recent builds available. Here is the DB entry:

go@tip
  environments: 
    /Users/aat/Projects/actor/bin: 2021-12-05T12:05:41+11:00
    /Users/aat/Projects/assert/bin: 2021-12-06T10:21:54+11:00
    /Users/aat/Projects/atomic/bin: 2021-12-04T16:01:01+11:00
    /Users/aat/Projects/concurrent/bin: 2021-12-05T07:22:41+11:00
    /Users/aat/Projects/entity/bin: 2021-12-05T17:52:35+11:00
    /Users/aat/Projects/hermit-packages/bin: 2021-12-01T14:46:09+11:00
    /Users/aat/Projects/sync/bin: 2021-12-04T14:35:37+11:00
    /Users/aat/Projects/traits/bin: 2021-12-04T15:50:00+11:00
  etag: "0e6cd7d6d696fdabfb3f44641e228104-27"
  updateCheckedAt: 2021-12-06T10:16:30+11:00
  usedAt: 2021-12-06T10:21:54+11:00

Here is the current ETag:

$ curl -s -L -I https://github.com/cashapp/hermit-build/releases/download/gotip/go-tip-darwin-arm64.tbz | grep -i etag
etag: "0x8D9B7EBB4BD5F6A"
``