chore(deps): Bump actions/checkout from 3 to 6 in /.github/workflows

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...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] <[email protected]>

Author: dependabot[bot]

.github/workflows/ci_freshness.yml

@@ -12,7 +12,7 @@ jobs:
   ci-freshness:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Install Rust
         uses: actions-rust-lang/[email protected]
       - name: Generate docs.yml

.github/workflows/contributors.yml

@@ -11,7 +11,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Check PR author in CONTRIBUTORS.md
         run: |
           pr_author=$(jq -r .pull_request.user.login "$GITHUB_EVENT_PATH")

.github/workflows/deny.yml

@@ -19,7 +19,7 @@ jobs:
           - advisories
           - licenses
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: EmbarkStudios/cargo-deny-action@v2
         with:
           command: check ${{ matrix.checks }}

.github/workflows/deploy_docs.yml

@@ -13,7 +13,7 @@ jobs:
     permissions:
       contents: write
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
           token: ${{ secrets.GITHUB_TOKEN }}