fix remove members stub url
fix remove members stub url

- stub url didn't match expect url so it was requiring discourse to be running or the test would fail
- use stub_delete
- use a_delete

spatten/discourse_api,techAPJ/discourse_api,oblakeerickson/discourse_api,maclover7/discourse_api,discourse/discourse_api,jmay/discourse_api,RyzacInc/discourse_api,Odyl/discourse_api,melissawahnish/discourse_api