uses-long-cache is too strict

The audit `uses-long-cache` is too restrictive as it basically requires a cache set to a value larger than 96.5 days to pass.

See https://github.com/GoogleChrome/lighthouse/blob/master/lighthouse-core/audits/byte-efficiency/uses-long-cache-ttl.js#L35

If instead the threshold was decreased to >= 90%. Then an asset cached for a week would be ok.