chore(deps): bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v4...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/system.yml

@@ -7,7 +7,7 @@ jobs:
     outputs:
       matrix: ${{ steps.make.outputs.matrix }}
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - id: make
         run: |
           if ! matrix_output=$(tests/generate_matrix.sh 2>&1); then
@@ -26,7 +26,7 @@ jobs:
       matrix: ${{ fromJson(needs.generate.outputs.matrix) }}
     steps:
       - name: Check out code into the Go module directory
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up Go
         uses: actions/setup-go@v6