Require Faraday 2.0.1 or greater (#554)

Faraday version 2.0.0 had a bug that resulted in no default adapter being instantiated. This was fixed in version 2.0.1 - lostisland/faraday@5f88f8f

Author: anrich

slack-ruby-client.gemspec

@@ -17,7 +17,7 @@ Gem::Specification.new do |s|
   s.homepage = 'http://github.com/slack-ruby/slack-ruby-client'
   s.licenses = ['MIT']
   s.summary = 'Slack Web and RealTime API client.'
-  s.add_dependency 'faraday', '>= 2.0'
+  s.add_dependency 'faraday', '>= 2.0.1'
   s.add_dependency 'faraday-mashify'
   s.add_dependency 'faraday-multipart'
   s.add_dependency 'gli'