ci: bump actions/checkout from 4.2.2 to 7.0.1

Bumps [actions/checkout](https://github.com/actions/checkout) from 4.2.2 to 7.0.1.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@11bd719...3d3c42e)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: 7.0.1
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/validate.yml

@@ -14,7 +14,7 @@ jobs:
     steps:
       # Pinned to a commit SHA rather than a mutable tag, per DSB-SC-002.
       # This repository applies its own rules.
-      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
 
       - uses: actions/setup-python@0b93645e9fea7318ecaed2b359559ac225c90a2b # v5.3.0
         with: