update gh-pages workflow

.github/workflows/gh-pages.yaml

@@ -12,8 +12,8 @@ jobs:
         run: |
           python -m pip install --upgrade pip
           pip install -r docs/requirements.txt
-          pip install xmltodict
-          pip install sophosfirewall-python
+          pip install ansible
+          ansible-galaxy collection install sophos.sophos_firewall
       - name: Sphinx build
         run: |
           bash docs/build.sh