chore(deps): bump actions/checkout

Bumps the all-actions-version-updates group with 1 update: [actions/checkout](https://github.com/actions/checkout).


Updates `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
  dependency-group: all-actions-version-updates
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
     name: Test
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - if: github.event_name != 'release' && github.event_name != 'workflow_dispatch'
         uses: Swatinem/rust-cache@v2
       - uses: taiki-e/install-action@v2
@@ -27,7 +27,7 @@ jobs:
     name: Test MSRV
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - if: github.event_name != 'release' && github.event_name != 'workflow_dispatch'
         uses: Swatinem/rust-cache@v2
       - uses: taiki-e/install-action@v2
@@ -46,7 +46,7 @@ jobs:
     if: github.event_name != 'release'
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: Swatinem/rust-cache@v2
       - uses: taiki-e/install-action@v2
         with: { tool: 'just,cargo-llvm-cov' }
@@ -88,7 +88,7 @@ jobs:
       group: release-plz-${{ github.ref }}
       cancel-in-progress: false
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with: { fetch-depth: 0 }
       - uses: dtolnay/rust-toolchain@stable
       - name: Publish to crates.io if crate's version is newer