Increase upper dependency for faraday (#196)

* Add upper dependency for faraday < 2.9

faraday 2.9 removes support for ruby 2.7

Author: kmymtksh

ads_common/google-ads-common.gemspec

@@ -35,7 +35,7 @@ Gem::Specification.new do |s|
   s.rubyforge_project = 'google-ads-common'
   s.require_path = 'lib'
   s.files = Dir.glob('lib/**/*') + %w(README.md ChangeLog)
-  s.add_runtime_dependency('faraday', '>= 0.9', '< 2.0')
+  s.add_runtime_dependency('faraday', '>= 0.9', '< 2.9')
   s.add_runtime_dependency('google-ads-savon', '~> 1.0', '>=1.0.2')
   s.add_runtime_dependency('httpi', '~> 2.3')
   s.add_runtime_dependency('httpclient', '~> 2.7')