Bump actions/checkout from 4 to 5

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 5.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v5)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/pages.yml

@@ -53,7 +53,7 @@ jobs:
         working-directory: docs
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
       - name: Setup Ruby
         uses: ruby/setup-ruby@v1
         with:

.github/workflows/publications.yml

@@ -34,7 +34,7 @@ jobs:
         working-directory: docs/about-issm/publications
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
       - name: Generate Publications Page
         run: |
           ./bin/generate_publications_page.sh > ${{ env.TARGET }}