Python3 is already available

.github/workflows/ci.yml

@@ -13,11 +13,6 @@ jobs:
       - name: Retrieve source code
         uses: actions/checkout@v3
 
-      - name: Setup python 3.9
-        uses: actions/setup-python@v3
-        with:
-          python-version: '3.9'
-
       - name: Install packages
         run: |
           brew update