refactor: replace deprecated StandardClaims with RFC7519-compliant RegisteredClaims

What does this MR do?

Bump golang-jwt/jwt to v4.1.0 and replace deprecated StandardClaims with RFC7519-compliant RegisteredClaims.

See https://github.com/golang-jwt/jwt/pull/15
See https://github.com/golang-jwt/jwt/issues/11

TODO

• I added the Changelog trailer (e.g. Changelog: feature) to the commits that need to be included in the changelog
• I added unit tests or they are not required
• I added acceptance tests or they are not required
• I added documentation (or it's not required)
• I followed code review guidelines
• I followed Go Style guidelines