Rule source on GitHub

DowngradeTypedClassConstRector

Remove typed class constant

 final class SomeClass
 {
-    public string FOO = 'test';
+    /**
+     * @var string
+     */
+    public FOO = 'test';
 }

Configure your rector.php:

<?php

use Rector\Config\RectorConfig;
use Rector\DowngradePhp83\Rector\ClassConst\DowngradeTypedClassConstRector;

return RectorConfig::configure()
    ->withRules([
        DowngradeTypedClassConstRector::class,
    ]);