Bump actions/checkout from 4 to 6.0.2

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.0.2.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v6.0.2)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: 6.0.2
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -10,7 +10,7 @@ jobs:
     permissions:
       contents: read
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6.0.2
         with:
           persist-credentials: false
       - uses: shivammathur/setup-php@7c071dfe9dc99bdf297fa79cb49ea005b9fcadbc  # v2.37.1, 2026-05-14