Rule source on GitHub

DowngradeFinalizePublicClassConstantRector

Remove final from class constants

 class SomeClass
 {
-    final public const NAME = 'value';
+    public const NAME = 'value';
 }

Configure your rector.php:

<?php

use Rector\Config\RectorConfig;
use Rector\DowngradePhp81\Rector\ClassConst\DowngradeFinalizePublicClassConstantRector;

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