It makes very little sense to duplicate named classes and modules.

Before:

```ruby
hash = { class: Object, module: Kernel }
hash.deep_dup # => {:class=>#<Class:0x00000001063ffc80>, :module=>#<Module:0x00000001063ffa00>}
```

After:

```ruby
hash = { class: Object, module: Kernel }
hash.deep_dup # => {:class=>Object, :module=>Kernel}
```