Update CI config.

Author: mblayman

.github/workflows/tests.yml

@@ -7,14 +7,14 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        python: [3.9, '3.10', 'pypy-3.7']
+        python: ['3.9', '3.10', '3.11', '3.12', '3.13']
         os: [macos-latest, ubuntu-latest, windows-latest]
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - name: Setup Python
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python }}