Fix a test failure using Ruby 3.3.0dev

[koic]

Description

This PR fixes the following test failure using Ruby 3.3.0dev:

$ ruby -v
ruby 3.3.0dev (2023-08-14T15:48:39Z master 52837fcec2) [x86_64-darwin22]
$ bundle exec rspec spec/faraday_spec.rb

Randomized with seed 57031

Faraday
  has a version number
  proxies to default_connection
    uses method_missing on Faraday if there is no proxyable method (FAILED - 1)
    proxies methods that exist on the default_connection
    proxied methods can be accessed

Failures:

  1) Faraday proxies to default_connection uses method_missing on Faraday if there is no proxyable method
     Failure/Error:
       expect { Faraday.this_method_does_not_exist }.to raise_error(
         NoMethodError, expected_message
       )

       expected NoMethodError with "undefined method `this_method_does_not_exist' for Faraday:Module",
       got #<NoMethodError: undefined method `this_method_does_not_exist' for module Faraday> with backtrace:
         # ./lib/faraday.rb:147:in `method_missing'
         # ./spec/faraday_spec.rb:27:in `block (4 levels) in <top (required)>'
         # ./spec/faraday_spec.rb:27:in `block (3 levels) in <top (required)>'
     # ./spec/faraday_spec.rb:27:in `block (3 levels) in <top (required)>'

That error message has been changed by https://github.com/ruby/ruby/commit/e7b8d32e in Ruby 3.3.0dev.

cf. https://bugs.ruby-lang.org/issues/18285

So the test error message is changed:

Ruby 3.2 or lower:

undefined method `this_method_does_not_exist' for Faraday:Module

Ruby 3.3.0dev:

NoMethodError: undefined method `this_method_does_not_exist' for module Faraday

Todos

List any remaining work that needs to be done, i.e:

• [x] Tests
• [x] Documentation

Additional Notes

N/A