lint: concept{s, exercises}: consider only warning when concept exercises are active

[ee7]

Currently configlet lint produces an error for a problem with a Concept or a Concept Exercise, even when concept exercises are not active.

It could instead produce only a warning when e.g.:

• status.concept_exercises is false in the track config.json file
• or when a concept exercise has a status that is not "active"

Follow-up from https://github.com/exercism/exercism/issues/5681#issuecomment-1122861507

This currently affects Julia the most.