Their release notes are here: https://github.com/golang-jwt/jwt/releases
Seemed wise to upgrade before we do even more with JWTs. For example
this upgrade *would* have mattered if we already implemented common JWT
claims such as expiration. Since we didn't rely on any claim
verification this upgrade is a noop...
...except for 1 test that called `Claims.Valid()`! Removing that
assertion *seems* scary, but it didn't actually do anything because we
didn't implement any of the standard claims it validated:
https://github.com/golang-jwt/jwt/blob/v4.5.0/map_claims.go#L120-L151
So functionally this major upgrade is a noop.
