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] <[email protected]>

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ jobs:
         runs-on: ubuntu-20.04
         steps:
             - name: Checkout
-              uses: actions/checkout@v3
+              uses: actions/checkout@v4
 
             - name: Set up PHP
               uses: shivammathur/setup-php@v2
@@ -51,7 +51,7 @@ jobs:
         runs-on: ubuntu-20.04
         steps:
             - name: Checkout
-              uses: actions/checkout@v3
+              uses: actions/checkout@v4
 
             - name: Set up PHP
               uses: shivammathur/setup-php@v2
@@ -97,7 +97,7 @@ jobs:
             fail-fast: false
         steps:
             - name: Checkout
-              uses: actions/checkout@v3
+              uses: actions/checkout@v4
 
             - name: Set up PHP
               uses: shivammathur/setup-php@v2