make tests work on gitlab again

.gitlab-ci.yml

@@ -4,9 +4,11 @@ test:
         - python3 -m ebpfcat.ebpf_test -v Tests && python3 -m ebpfcat.ethercat_test -v
 
 docs:
-    image: tk0miya/sphinx-html
+    image: sphinxdoc/sphinx
     script:
-        - python3 setup.py install --user
+        - apt-get update
+        - apt-get install -y openssh-client
+        - pip3 install . --user
         - sphinx-build -b html -d _build/doctrees . _build/html
         - eval $(ssh-agent)
         - echo "$SSHKEY" | ssh-add -