build(deps): bump actions/checkout from 3 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [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/v3...v4)

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

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

.github/dependabot.yml

@@ -4,8 +4,10 @@ updates:
     directory: "/"
     schedule:
       interval: "daily"
+      timezone: "Europe/Helsinki"
 
   - package-ecosystem: "github-actions"
     directory: "/"
     schedule:
       interval: "daily"
+      timezone: "Europe/Helsinki"

.github/workflows/html5validator.yml

@@ -7,7 +7,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3 # Required will all actions
+      - uses: actions/checkout@v4 # Required will all actions
 
       - uses: ruby/setup-ruby@v1
         with: