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

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/build.yml

@@ -29,7 +29,7 @@ jobs:
       _R_CHECK_CRAN_INCOMING_REMOTE_: false
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: r-lib/actions/setup-r@v2
       with:
         r-version: ${{ matrix.r }}

.github/workflows/pkgdown.yml

@@ -10,7 +10,7 @@ jobs:
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: fregante/setup-git-user@v2
     - uses: r-lib/actions/setup-pandoc@v2
     - uses: r-lib/actions/setup-r@v2

.github/workflows/upstream.yml

@@ -25,7 +25,7 @@ jobs:
       CHECK_VERSION: ${{ matrix.version }}
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         repository: r-quantities/quantities
         fetch-depth: 0