build(deps): Bump actions/checkout from 3 to 4 (#18)

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] <[email protected]>

.github/workflows/continuous-delivery.yml

@@ -38,7 +38,7 @@ jobs:
         echo "E2E_PRE_ROLLING_UPDATE_IMG=${e2e_pre_rolling_update_image}" >> $GITHUB_OUTPUT
 
     - name: Checkout Code
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
 
     - name: Log in to the GitHub Container registry
       uses: docker/login-action@v3
@@ -105,7 +105,7 @@ jobs:
           echo "-----------------------------------------------------"
 
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           repository: cloudnative-pg/cloudnative-pg
           ref: main