Bump actions/checkout from 2 to 4 (#1044)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v4)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/continuous-integration.yml

@@ -21,7 +21,7 @@ jobs:
       matrix:
         php-version: [ '5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3' ]
     steps:
-      - uses: "actions/checkout@v2"
+      - uses: "actions/checkout@v4"
       - uses: "shivammathur/setup-php@v2"
         with:
           php-version: "${{ matrix.php-version }}"
@@ -36,7 +36,7 @@ jobs:
     name: "Coding Standards"
     runs-on: "ubuntu-latest"
     steps:
-      - uses: "actions/checkout@v2"
+      - uses: "actions/checkout@v4"
       - uses: "shivammathur/setup-php@v2"
         with:
           php-version: "latest"
@@ -51,7 +51,7 @@ jobs:
     name: "Coverage"
     runs-on: "ubuntu-latest"
     steps:
-      - uses: "actions/checkout@v2"
+      - uses: "actions/checkout@v4"
       - uses: "shivammathur/setup-php@v2"
         with:
           php-version: "latest"
@@ -74,7 +74,7 @@ jobs:
       matrix:
         php-version: [ '5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3' ]
     steps:
-      - uses: "actions/checkout@v2"
+      - uses: "actions/checkout@v4"
       - uses: "shivammathur/setup-php@v2"
         with:
           php-version: "${{ matrix.php-version }}"