[DeadCode] Skip RemoveParentDelegatingConstructorRector on protected parent constructor

[TomasVotruba]

Fixes rectorphp/rector#9842

The rule checked that the child constructor is public, but never checked the parent's visibility. Removing a public constructor that delegates to a protected parent one silently narrows visibility and breaks instantiation:

Fatal error: Uncaught Error: Call to protected A::__construct() from global scope

Buggy behavior before this PR:

 class A
 {
     protected function __construct($value)
     {
     }
 }

 class B extends A
 {
-    public function __construct($value)
-    {
-        parent::__construct($value);
-    }
 }

 new B('value'); // fatal error after the change

Now the rule bails out when the parent constructor is not public, so the code above is left untouched.