chore(deps): update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/testing.yaml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Install dependencies
         run: go mod download
       - name: Execute golang tests