ci: Update GitHub actions revs for php-ci (#1360)

Follow-up to #1356.

Author: svix-jplatte

.github/workflows/php-ci.yml

@@ -16,9 +16,9 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: PHPUnit Tests
-        uses: php-actions/phpunit@v3
+        uses: php-actions/phpunit@v4
         with:
           version: latest
           configuration: "php/phpunit.xml"