Consider setting up lifecycle policies for the "secrets logging" bucket

[alexwlchan]

Currently we have two buckets for Buildkite: secrets and secrets-logging.

The second bucket logs all access to the secrets in the first, but these logs go back a long way – to the beginning of our use of Buildkite, in 2020. It seems unlikely we'd ever need to look at secrets going that far back, and we should consider applying some sort of lifecycle retention policy to the logging bucket, e.g. deleting access logs 90 days after they were created.