Bump actions/checkout from 5.0.0 to 6.0.0

Bumps [actions/checkout](https://github.com/actions/checkout) from 5.0.0 to 6.0.0.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5.0.0...v6.0.0)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: 6.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/test.yml

@@ -4,7 +4,7 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5.0.0
+      - uses: actions/checkout@v6.0.0
       - uses: cachix/install-nix-action@v31
         with:
           nix_path: nixpkgs=channel:nixos-unstable

.github/workflows/update.yml

@@ -7,7 +7,7 @@ jobs:
   update-sources:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5.0.0
+      - uses: actions/checkout@v6.0.0
       - uses: cachix/install-nix-action@v31
         with:
           nix_path: nixpkgs=channel:nixos-unstable