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/merge-main.yml

@@ -22,7 +22,7 @@ jobs:
       contents: read
       security-events: write
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Initialize
         uses: github/codeql-action/init@v2

.github/workflows/pr-open.yml

@@ -52,7 +52,7 @@ jobs:
             build_file: ./frontend/Dockerfile.app
             build_context: ./frontend
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: bcgov-nr/action-builder-ghcr@v1.1.2
         with:
           package: ${{ matrix.package }}

.github/workflows/unit-tests.yml

@@ -48,7 +48,7 @@ jobs:
     if: github.event_name != 'pull_request' || !github.event.pull_request.draft
     runs-on: ubuntu-22.04
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Run Trivy vulnerability scanner in repo mode
         uses: aquasecurity/trivy-action@0.11.2