fix for CI fix

Author: codemasher

.github/workflows/ci.yml

@@ -145,7 +145,9 @@ jobs:
           coverage: none
 
       - name: "Install Sphinx"
-        run: pipx install --include-deps sphinx myst-parser sphinx-rtd-theme
+        run: |
+          python -m venv ci-venv
+          ci-venv/bin/pip install sphinx myst-parser sphinx-rtd-theme
 
       - name: "Install dependencies with composer"
         uses: ramsey/composer-install@v3