Clarify build step

Author: arnaudlimbourg

.github/workflows/ci.yml

@@ -12,7 +12,7 @@ jobs:
     steps:
       - uses: actions/checkout@v2
 
-      - name: Set up Python 3.9
+      - name: Set up Python
         uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}