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](actions/checkout@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/workflows/ci.yml

@@ -52,7 +52,7 @@ jobs:
         uses: alphagov/govuk-infrastructure/.github/actions/setup-redis@main
 
       - name: Checkout repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Setup Ruby
         uses: ruby/setup-ruby@v1

.github/workflows/copy-pr-template-to-dependabot-prs.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     if: github.actor == 'dependabot[bot]'
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Post PR template as a comment
         uses: actions/github-script@v6

.github/workflows/pact-verify.yml

@@ -49,7 +49,7 @@ jobs:
       TEST_DATABASE_URL: postgresql://postgres@localhost/test-db
       RAILS_ENV: test
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           repository: alphagov/link-checker-api
           ref: ${{ inputs.ref }}