don't use broken action

.github/workflows/documentation.yaml

@@ -21,12 +21,13 @@ jobs:
       uses: psf/black@stable
       with:
           version: "23.7.0"
-    # Standard drop-in approach that should work for most people.
-    - name: Build docs
-      uses: ammaraskar/sphinx-action@master
-      with:
-        pre-build-command: "apt-get --allow-releaseinfo-change update -y && apt-get install -y g++ && apt-get install -y gfortran && apt-get install -y git"
-        docs-folder: "docs/"
+    - name: Upgrade pip, install package, install requirements, build docs
+      run: |
+        pip install --upgrade pip
+        pip install .
+        pip install -r ./docs/requirements.txt
+        pip install sphinx
+        sphinx-build docs ./docs/_build/html/
     - name: Checkout pages branch
       uses: actions/checkout@v4
       with: