Fix publishing docs (#284)

Fix "Version 3.7 was not found in the local cache".

.github/workflows/docs.yml

@@ -18,7 +18,7 @@ jobs:
       - name: Setup Python
         uses: actions/setup-python@v5
         with:
-          python-version: 3.7
+          python-version: '3.x'
       - name: Install Tox
         run: pip install tox
       - name: Run Tox