Update check-docs.yml

.github/workflows/check-docs.yml

@@ -43,6 +43,7 @@ jobs:
         run: |
           python -m pip install --upgrade pip
           python -m pip install pandoc
+          python -m pip install git+https://github.com/cea-cosmic/modopt@develop # Workaround, to be removed
           python -m pip install -r docs/requirements.txt
           python -m pip install .