Go packages: Disable MD5 in FIPS mode

I think this feature is behind a feature flag, but we still do this. In FIPS mode (Gitlab::FIPS.enabled?), we must disable/remove the use of MD5 completely.

I see in https://gitlab.com/gitlab-org/gitlab/blob/c5c0318740fb5017b950a96ce8878712f99af905/app/services/packages/go/create_package_service.rb#L41 we compute the MD5.

We should disable this in FIPS mode.