Bump actions/checkout from 2 to 3 (#8)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 3.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v3)

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

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

Author: dependabot[bot]

.github/workflows/php.yml

@@ -15,7 +15,7 @@ jobs:
       matrix:
         php-version: [ '7.4', '8.0', '8.1' ]
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - name: Use PHP ${{ matrix.php-version }}
       uses: shivammathur/setup-php@v2
       with: