https://gitlab.com/gitlab-org/gitlab/-/merge_requests/117468 in GitLab
15.11 updated the ruby-jwt gem to v2.5.0. In v2.2.0, ruby-jwt removed
the `iat_leeway` parameter (https://github.com/jwt/ruby-jwt/pull/274).

As a result, if a gitlab-shell host creates a JWT token with an
issued-at (IAT) claim that is slightly behind the host handling API
the request, users will receive a 401 error.

Disable this IAT verification by default since it's not serving a
useful purpose, since expiration times are already validated. We
already made a similar change in Geo.

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/417543

Changelog: fixed