Use setup-python@v6 to support free-threaded Python

Author: bowiechen

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
       - name: Setup python
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v6
         with:
           python-version: ${{ matrix.python }}
           allow-prereleases: true
@@ -46,7 +46,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
       - name: Setup python
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v6
         if: "!endsWith(matrix.python, '-dev')"
         with:
           python-version: ${{ matrix.python }}
@@ -76,7 +76,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
       - name: Setup python
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v6
         with:
           python-version: ${{ matrix.python }}
           allow-prereleases: true