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/workflows/tests.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
     - name: Validate composer.json and composer.lock
       run: composer validate
     - name: Install dependencies
@@ -29,7 +29,7 @@ jobs:
 
     # let's get started!
     - name: Checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
 
     # cache PHP extensions
     - name: Setup cache environment
@@ -99,7 +99,7 @@ jobs:
     steps:
 
     - name: Checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
 
     - name: Setup Node
       uses: actions/setup-node@v3