* ruby33.y: extract words_sep

[iliabylich]

Closes #923.

This is a Ripper-only change + minor refactoring. Here's a test code from the commit:

p %w(

w
 w w )

Ruby 3.2.2:

$ ruby -v test.rb
ruby 3.2.2 (2023-03-30 revision e51014f9c0) [arm64-darwin23]
["w", "w", "w"]

Ruby 3.3.0:

$ ruby -v test.rb
ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [arm64-darwin23]
["w", "w", "w"]