Modified workflow for doc

.github/workflows/documentation.yml

@@ -9,7 +9,7 @@ jobs:
       - name: Install dependencies
         run: |
           pip install sphinx sphinx_rtd_theme sphinx-copybutton
-          pip install elevation_mapping_cupy/.
+          pip install -r elevation_mapping_cupy/requirements.txt
       - name: Sphinx build
         run: |
           sphinx-build docs/source docs/_build