[DowngradePhp81] Handle parent is void on DowngradeNeverTypeDeclarationRector

[samsonasik]

@kkmuffme this should can handle:

• DowngradeNeverTypeDeclarationRector creates a fatal error bc never type hint is removed rector#9334

For note, this kind of tweak should not needed actually per se, as child should follow parent, that can easily error if not follow, eg: on native mixed with child never;

https://3v4l.org/dYEAF

which cannot just converted to void

https://3v4l.org/fWSJJ

which make error :)

[samsonasik]

All checks have passed 🎉 @TomasVotruba I am merging it ;)