Bump actions/checkout from 2 to 4 (#241)

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/tests.yml

@@ -64,7 +64,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout source
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - name: Set up Python 3.8
         uses: actions/setup-python@v5
         with: