CI: use GH action to install Redis

Author: dmgav

.github/workflows/docs_publish.yml

@@ -22,6 +22,9 @@ jobs:
       uses: actions/setup-python@v2
       with:
         python-version: ${{ matrix.python-version }}
+    - uses: shogo82148/actions-setup-redis@v1
+      with:
+        redis-version: "7.x"
     - name: Install dependencies
       run: |
         sudo apt install redis