Update .gitlab-ci.yml file

.gitlab-ci.yml

@@ -269,7 +269,8 @@ pages:
   script:
   - pip install -U sphinx
   - python3 -m pip install nbsphinx --user
-  - sphinx-build -b html ./docs ./docs/_build
+  - cd docs
+  - make html
   artifacts:
     paths:
     - ./docs/_build