Bump actions/checkout from 5 to 6 (#11)

Author: dependabot[bot]

.github/workflows/test.yaml

@@ -20,7 +20,7 @@ jobs:
         ujson: [false, true]
     steps:
       - name: Check out github
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v6