Temporarily remove 3.6 testing
The current 3.6 docker build appears to be broken. This merge request temporarily removes the 3.6 test pipeline before the upcoming release. https://hub.docker.com/repository/docker/bilbydev/v2-dockerfile-test-suite-python36/general
This also means other MRs can be merged if they only fail the 3.6 test pipeline
Edited by Moritz Huebner