Use actions/checkout@v3

Author: OskarStark

examples/.github/workflows/test.yml

@@ -12,7 +12,7 @@ jobs:
 
     steps:
         - name: "Checkout"
-          uses: actions/checkout@v2
+          uses: actions/checkout@v3
 
         - name: PHPStan
           uses: docker://oskarstark/phpstan-ga