This should allow consumers to see deprecation warnings that correctly
mention the next version of VC.

Co-Authored-By: Elia Schito <elia@schito.me>
Co-Authored-By: Hans Lemuet <Spone@users.noreply.github.com>

```
lib/view_component/polymorphic_slots.rb:42: warning: method redefined; discarding old header
lib/view_component/polymorphic_slots.rb:42: warning: previous definition of header was here
lib/view_component/polymorphic_slots.rb:42: warning: method redefined; discarding old items
lib/view_component/polymorphic_slots.rb:42: warning: previous definition of items was here
```

…mplate

Was generating this warning:

```
test/sandbox/app/components/jbuilder_component.json.jbuilder:1: warning: `frozen_string_literal' is ignored after any tokens
```

See also: https://bugs.ruby-lang.org/issues/16602

Co-authored-by: Cameron Dutro <camertron@github.com>