ci: remove sphinx theme and plugins not used

.gitlab-ci.yml

@@ -19,7 +19,6 @@ test:docs:
     - cp config.yaml.example config.yaml
     - apt update && apt install build-essential
     - pip install -r requirements.txt
-    - pip install -U sphinx sphinx-press-theme sphinx-jsonschema
     - pushd docs && DISABLE_METRICS=true sphinx-build -b html . ../public && popd
   rules:
     - if: $CI_COMMIT_REF_NAME != $CI_DEFAULT_BRANCH