Bump actions/checkout from 5 to 7

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 7.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v5...v7)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/link-check.yml

@@ -22,7 +22,7 @@ jobs:
     name: Check links
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v7
 
       - name: Check links
         id: lychee

.github/workflows/markdown-lint.yml

@@ -17,7 +17,7 @@ jobs:
     name: Markdown lint
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v7
 
       - uses: DavidAnson/markdownlint-cli2-action@v19
         with:
@@ -27,7 +27,7 @@ jobs:
     name: README conventions
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v7
 
       - name: Check entry format and duplicates
         run: python3 .github/scripts/check_readme.py