[CodingStyle] Skip private parent methods in MakeInheritedMethodVisibilitySameAsParentRector

[TomasVotruba]

Bug

MakeInheritedMethodVisibilitySameAsParentRector narrows a child method's visibility to match a private parent method of the same name. But private methods are not inherited — the child method does not override them, so there is no inheritance relationship and no reason to align visibility.

class ParentClassWithPrivateMethod
{
    private function run() {}
}

class PrivateClassParent extends ParentClassWithPrivateMethod
{
    public function run() {}   // independent public method, unrelated to the parent's private run()
}

The rule rewrote the child to private function run(), silently removing it from the public API even though PHP places no visibility constraint between a private parent method and a same-named child method.

Fix

Skip private parent methods when aligning visibility (they are not inherited). The now-unreachable private branches in the two helpers are removed.

The previous private.php.inc fixture encoded the buggy narrowing as expected output; it becomes a no-change fixture (skip_private_parent_method.php.inc).

Protected/public parent behavior is unchanged.