Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/nix-integration-test.yml

@@ -11,7 +11,7 @@ jobs:
     name: Build
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@0c366fd6a839edf440554fa01a7085ccba70ac98 # v4.1.1
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
       - uses: cachix/install-nix-action@51f3067b56fe8ae331890c77d4e454f6d60615ff # v31.10.2
         with:
           extra_nix_config: |