Disable https_check for local environments

[jiturriagaAB]

I'm currently working with a local okta server on my machine which obviously doesn't use https, however there's no way to disable the https_check from within my code.

okta-jwt-verifier-python/okta_jwt_verifier/config_validator.py

Line 24 in a43bd2f

self.validate_issuer()

It seems like a fairly straight forward fix to allow the user to change https_check for the config validator.

[forzagreen]

For information, the https check can be disabled in https://github.com/okta/okta-sdk-python with the environment variable OKTA_TESTING_TESTINGDISABLEHTTPSCHECK

It would be great if this option is added here.

Ref: https://github.com/okta/okta-sdk-python#environment-variables