Update to actions/checkout@v3 because of Node.js 12 deprecation

https://github.blog/changelog/2022-09-22-github-actions-all-actions-will-begin-running-on-node16-instead-of-node12/

Author: spaze

.github/workflows/php.yml

@@ -14,7 +14,7 @@ jobs:
           - "8.1"
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: OS info
       run: cat /etc/os-release