Ruby 4 compatability

[arielvalentin]

🎉 https://www.ruby-lang.org/en/news/2025/12/25/ruby-4-0-0-released/ 🎉

There are several warnings that appear when running specs warning us about upcoming changes that we will need to address when we upgrade to Ruby 4.

E.g.

opentelemetry-api-1.7.0/lib/opentelemetry/baggage/propagation/text_map_propagator.rb:7: warning: CGI library is removed from Ruby 4.0. Please use cgi/escape instead for CGI.escape and CGI.unescape features.

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