[CI] Disable Selenium tests for now due to lack of network support in GitLab CI

cf. https://gitlab.com/gitlab-org/gitlab-runner/issues/1042

.gitlab-ci.yml

@@ -56,6 +56,10 @@ test_wheel:
   stage: test
   image:
     name: registry.edugit.org/teckids/docker-images/python-pimped:master
+  services:
+    - selenium/hub
+    - selenium/node-chrome
+    - selenium/node-firefox
   before_script:
     - adduser --disabled-password --gecos "Test User" testuser
     - mkdir -p screenshots && chown testuser screenshots