build(deps): bump actions/checkout from 5 to 7

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 7.
- [Release notes](https://github.com/actions/checkout/releases)
- [Commits](https://github.com/actions/checkout/compare/v5...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>

.github/workflows/docker_linux.yml

@@ -47,7 +47,7 @@ jobs:
       IMAGE_TAG: ghcr.io/${{ github.repository }}/apache-nuttx-ci-linux
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
 
       - name: Free Disk Space (Ubuntu)
         uses: ./.github/actions/free-disk-space