ruby/syntax_suggest@ce7b87184e

ruby/syntax_suggest@54bb8ab330

It used to not emit this token type, but now it does.
So when a newer version of prism is present, we can fall back
to the same code that ripper uses.

Ref:
* ruby#15914
* ruby/prism#3859

ruby/syntax_suggest@42a3b8f6cb

The reason this logic for different methods branches in the class instead of internally was to be eagerly aggressive about runtime performance. This code is currently only used once for the document where it's invoked ~N times (where N is number of lines):

```ruby
module SyntaxSuggest
  class CleanDocument
    # ...
    def join_trailing_slash!
      trailing_groups = @document.select(&:trailing_slash?).map do |code_line|
        take_while_including(code_line.index..) { |x| x.trailing_slash? }
      end
      join_groups(trailing_groups)
      self
    end
```

Since this is not currently a hot-spot I think merging the branches and using a case statement is a reasonable tradeoff and avoids the need to do specific version testing.

An alternative idea was presented in ruby#241 of behavior-based testing for branch logic (which I would prefer), however, calling the code triggered requiring a `DelegateClass` when the `syntax_suggest/api` is being required.

ruby/syntax_suggest@ab122c455f