build(deps): bump actions/checkout

Bumps the actions group in /.github/workflows 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: actions
...

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

Author: dependabot[bot]

.github/workflows/build-site.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check out the code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Fetch main
         run: |

.github/workflows/deploy-gh-pages.yml

@@ -32,7 +32,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Setup Ruby
         uses: ruby/setup-ruby@v1
         with:

.github/workflows/linkcheck.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check out the code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Fetch main
         run: |

.github/workflows/main.yml

@@ -11,7 +11,7 @@ jobs:
     name: Action lint
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Check workflow files
         run: |
           bash <(curl https://raw.githubusercontent.com/rhysd/actionlint/main/scripts/download-actionlint.bash)

.github/workflows/update-contribs-reviews.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check out the code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Setup Python
         uses: actions/setup-python@v6
         with: