ci: Use GitHub Actions V3 (php-debugbar#553)

Author: erikn69

.github/workflows/run-tests.yml

@@ -25,7 +25,7 @@ jobs:
 
     steps:
     - name: Checkout code
-      uses: actions/checkout@v2
+      uses: actions/checkout@v3
 
     - name: Setup PHP
       uses: shivammathur/setup-php@v2