Update test.yml, downgrade setup-python

@v5 -> @v4 try to fix https://github.com/Kozea/Radicale/issues/1503

.github/workflows/test.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-python@v5
+      - uses: actions/setup-python@v4
         with:
           python-version: ${{ matrix.python-version }}
       - name: Install Test dependencies