Bump actions/checkout from 2 to 3

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 3.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v3)

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

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

Author: dependabot[bot]

.github/workflows/check-urls.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
 
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Check link validity
         uses: lycheeverse/lychee-action@v1.5.0