fix: Downgrade code to PHP 7.3

Author: Nattfarinn

src/bundle/Core/Command/VirtualFieldDuplicateFixCommand.php

@@ -26,7 +26,8 @@ final class VirtualFieldDuplicateFixCommand extends Command
 
     private const DEFAULT_SLEEP = 0;
 
-    private Connection $connection;
+    /** @var \Doctrine\DBAL\Connection */
+    private $connection;
 
     public function __construct(
         Connection $connection