chore(deps): bump actions/checkout from 6 to 7

Bumps [actions/checkout](https://github.com/actions/checkout) from 6 to 7.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v6...v7)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/backport.yaml

@@ -15,7 +15,7 @@ jobs:
     # Don't run on closed unmerged pull requests
     if: github.event.pull_request.merged
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
       - name: Create backport pull requests
         uses: korthout/backport-action@v4
         with: