[DeadCode] `RemoveDeadConstructorRector` should not remove `private` construct

[stloyd]

Subject	Details
PHP version	any
Full Command	vendor/bin/rector process /src --set dead-code

Current Behaviour

Rector Rector\DeadCode\Rector\ClassMethod\RemoveDeadConstructorRector removes also private method, which should not be touched as it's done for purpose to not allow calls: new SomeClass().

-    private function __construct()
-    {
-    }
-
     public static function someMethod(): bool
     {

Minimal PHP Code Causing Issue

<?php

class SomeClass
{
     private function __construct()
     {
     }

     public static function forExampleFactoryMethod()
     {
         return new self();
     }
}

Expected Behaviour

No changes.

[TomasVotruba]

Good point! This is easy pick. Care for PR?