ci: upgrade actions/checkout from v4 to v6

Author: vistart

.github/workflows/test.yml

@@ -65,7 +65,7 @@ jobs:
 
     steps:
       - name: Check out the repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v5