Ruby 4 compatibility

[klevo]

On Ruby 4 the gem fails during initialization on line

openai-ruby/lib/openai/internal/util.rb

Line 275 in d4c2ae8

CGI.parse(query.to_s)

due to CGI.parse no longer being a method in Ruby 4.

This is probably due CGI library being removed from the default gems in Ruby 4 and adding it as a dependency should resolve it.

[klevo]

Thanks for merging the fix 👏