Bump actions/checkout from 5 to 6 (#47)

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
...

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

Author: dependabot[bot]

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

@@ -16,7 +16,7 @@ jobs:
       - run: echo "The job was automatically triggered by a ${{ github.event_name }} event."
       - run: echo "The name of your branch is ${{ github.ref }} and your repository is ${{ github.repository }}."
       - name: Check out repository code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - run: echo "The ${{ github.repository }} repository has been cloned to the runner."
       - name: Generate the files in docker
         run: scripts/run.sh

.github/workflows/clean-scratch-site.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check out repository code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Deploy ssh key for scratch site
         shell: bash -l {0}
         run: |