No DELETE path for challenge-types or challenge-tracks

[jmgasper]

There is no way to DELETE a challenge-type or challenge-track via the API. This means that there is an erroneous challenge-type in dev that was created but can't be deleted.

We need to support the DELETE verb for both challenge-types and challenge-tracks, restricted solely to admins.

Please ensure that you fully update:

• Code
• Postman
• Swagger
• Tests

To test

You should be able to get an admin token using jcori / Appirio123 in the dev environment.