Updated some GitHub Actions dependencies.

Author: Kodiologist

.github/workflows/tests.yaml

@@ -9,10 +9,10 @@ jobs:
     steps:
     - uses: actions/checkout@v6
     - uses: actions/setup-python@v6
-      with: {python-version: 3.14}
+      with: {python-version: '>=3.15.0-beta.1'}
     - run: pip install .
     - run: pip install pytest
-    - uses: actions/cache@v4
+    - uses: actions/cache@v5
       with:
         key: cache-dir
         path: .pytest_cache/d