Fix ruby 3.4 future frozen string warning

[william-stacken]

When updating to ruby 3.4.x in my rails project, I get warnings such as these

~/.ruby/gems/twitter_cldr-6.12.0/lib/twitter_cldr/formatters/formatter.rb:17: warning: literal string will be frozen in the future (run with --debug-frozen-string-literal for more information)
~/.ruby/gems/cldr-plurals-runtime-rb-1.1.0/lib/cldr-plurals/ruby-runtime/str_num.rb:44: warning: literal string will be frozen in the future (run with --debug-frozen-string-literal for more information)

This PR fixes the warnings, and removes the dependency on cldr-plurals-runtime-rb since I could not find the maintained repo for that gem, and it is small enough to simply copy into this gem. Let me know if you would prefer me to fix the warning inside that gem itself instead of removing the dependency on it.

[CLAassistant]

All committers have signed the CLA.

[camertron]

Hey @william-stacken, apologies for the delayed response, thanks for your PR 😄

The cldr-plurals-runtime-rb gem is hosted here and is maintained by me 😄 It hasn't received updates for quite a while because it simply doesn't need any - the CLDR plurals format has not (to my knowledge) changed very much over the past ~10 years or so.

Accordingly, please add the dependency back to the gemspec and remove the copied class 😄

[william-stacken]

Thanks @camertron! I have opened another PR for fixing the frozen string warning in the dependency here.

camertron/cldr-plurals-runtime-rb#3