test usage of 7.3

Author: s-martin

.github/workflows/php.yml

@@ -20,7 +20,7 @@ jobs:
     - name: Setup PHP with XDebug
       uses: shivammathur/setup-php@v2
       with:
-        php-version: 7.4
+        php-version: 7.3
         coverage: xdebug
         tools: composer