Updated GH docs job requirements

.github/workflows/documentation.yml

@@ -16,7 +16,8 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install -r requirements.txt
+          pip install sphinx
+          pip install furo
       - name: Sphinx build
         run: |
           cd docs && sphinx-build . _build