Fix colision of `:quarkus_config_url:`

Summary

Link to `:quarkus_config_url:` was redefined in `orchestration-of-openapi-based-services.adoc` (first defined in antora.yml) and later used to link to https://quarkus.io/guides/config-reference#with-environment-variables, which resulted in overwriting the link and linking to https://quarkus.io/guides/config#with-environment-variables instead. Used `:quarkus_config_reference_url:`instead.

Acceptance criteria

The link is now working correctly and another usage of `:quarkus_config_url:` is working as well.