Upgrade GH action version to remove warnings

Author: andrivet

.github/workflows/tests.yml

@@ -14,7 +14,7 @@ jobs:
         python-version: ['2.7', '3.5', '3.6', '3.7', '3.8', '3.9', '3.10', '3.11', '3.12']
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Set up Python ${{ matrix.python-version }}
       uses: LizardByte/setup-python-action@master
       with: