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/main.yml

@@ -30,10 +30,10 @@ jobs:
             host: ubuntu-24.04
             cc: clang
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
         with:
           path: tp_smapi
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
         with:
           repository: torvalds/linux
           ref: ${{ matrix.linux }}