Bump actions/checkout from 5 to 6 in the all group

Bumps the all group with 1 update: [actions/checkout](https://github.com/actions/checkout).


Updates `actions/checkout` from 5 to 6
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...v6)

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

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

Author: dependabot[bot]

.github/workflows/validate.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     name: "Validate landscape.yml file"
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: cncf/landscape2-validate-action@v2
         with:
           target_kind: data