Bump actions/checkout from 5 to 6 (#46)

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/rust.yml

@@ -14,7 +14,7 @@ jobs:
       checks: write
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Build
         run: cargo build
       - name: Run tests
@@ -28,7 +28,7 @@ jobs:
   format:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Format Rust code
         run: cargo fmt --all -- --check
 
@@ -37,7 +37,7 @@ jobs:
     env:
       RUSTC_BOOTSTRAP: 1
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Install cargo-llvm-cov
         uses: taiki-e/install-action@v2
         with: