Bump actions/checkout from 3 to 4 (#57)

Author: dependabot[bot]

.github/workflows/tests.yaml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Install Go
         uses: actions/setup-go@v4