`httpclient` dependency causing deprecation warnings about failure in Ruby 3.4.0

[aramprice]

The httpclient dependency of cf-uaa-lib hasn't had updates in 4+ years and using cf-uaa-lib on Ruby 3.3.x results in the following warnings:

~/.gem/ruby/3.3.5/gems/httpclient-2.8.3/lib/httpclient/auth.rb:11: warning: ~/.rubies/ruby-3.3.5/lib/ruby/3.3.0/mutex_m.rb was loaded from the standard library, but will no longer be part of the default gems starting from Ruby 3.4.0.
You can add mutex_m to your Gemfile or gemspec to silence this warning.
Also please contact the author of httpclient-2.8.3 to request adding mutex_m into its gemspec.

While a short term fix of adding mutex_m as a gem dependency will resolve the warning it might be prudent to switch to Ruby's standard HTTP client https://github.com/ruby/net-http since httpclient doesn't appear to be maintained any longer.

This was recently done in bosh: cloudfoundry/bosh#2557

[aramprice]

See also #101