Allow stevenmaguire/oauth2-keycloak v6 to fix CVE

[Huluti]

V6 of stevenmaguire/oauth2-keycloak is here and it fixes a CVE caused by firebase/php-jwt < 7.0.0:
https://github.com/stevenmaguire/oauth2-keycloak/tags

Would be good to release a new version that fix #59 and this issue 🙏

[mainick]

Hi @Huluti , I updated the library to Symfony 8.0 with PR #62

[Huluti]

Thanks a lot @mainick for maintaining this great bundle!