Fixes RT#90936  Class::MOP::load_class deprecation warnings

This fixes RT#90936: warnings produced by the deprecation of Class::MOP::load_class

See https://rt.cpan.org/Ticket/Display.html?id=90936

The only thing I'm unsure of is this bit: 
```perl
lib/Test/Sweet.pm:    if($meta->isa('Class::MOP::Class')){
```