build(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/build.yml

@@ -32,7 +32,7 @@ jobs:
       image: ghcr.io/flathub-infra/flatpak-github-actions:kde-6.10
       options: --privileged
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
       - uses: flatpak/flatpak-github-actions/flatpak-builder@master
         with:
           bundle: rare-${{ github.ref_name }}.flatpak