jwt: Update `go-jose/go-jose` to `v4` from `v3`

Library: https://github.com/go-jose/go-jose

v4.0.0 was release in Feb 2024 and it would therefore be nice to update cap's jwt implementation to use this version too.

The change would then allow Nomad (other likely too) to upgrade and remove its dependency on v3 of the library.