Version 6.0.0 still registers classes other than public when using `AddClasses(Action<IImplementationTypeFilter> action)`

[tomaszprasolek]

See the code: https://github.com/khellang/Scrutor/blob/de6ed9c34858061795bd753abe63881980d916c5/src/Scrutor/ImplementationTypeSelector.cs#L39C9-L39C54

[tomaszprasolek]

I made PR for this: #247