Ruby 3.4 deprecation warning

[fatkodima]

ruby/3.4.0/gems/httpclient-2.8.3/lib/httpclient/util.rb:71: warning: literal string will be frozen in the future (run with --debug-frozen-string-literal for more information)
ruby/3.4.0/gems/httpclient-2.8.3/lib/httpclient/http.rb:510: warning: literal string will be frozen in the future (run with --debug-frozen-string-literal for more information)

[pioz]

Same warning here with Ruby 3.4.

[yahonda]

httpclient 2.9.0 has been released that has #471