downgrade rack

Gemfile

@@ -5,6 +5,8 @@ git_source(:github) {|repo_name| "https://github.com/#{repo_name}" }
 # Specify your gem's dependencies in yandex-checkout.gemspec
 gemspec
 
+gem 'evil-client', git: 'https://github.com/paderinandrey/evil-client.git'
+
 group :development, :test do
   gem 'pry',        platform: :mri
   gem 'pry-byebug', platform: :mri

yandex-checkout.gemspec

@@ -1,5 +1,6 @@
+# frozen_string_literal: true
 
-lib = File.expand_path('../lib', __FILE__)
+lib = File.expand_path('lib', __dir__)
 $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 require 'yandex-checkout/version'
 
@@ -21,8 +22,6 @@ Gem::Specification.new do |spec|
 
   spec.required_ruby_version = '>= 2.5'
 
-  spec.add_runtime_dependency 'evil-client', '~> 3.0'
-
   spec.add_development_dependency 'rake', '>= 10.0'
   spec.add_development_dependency 'rspec', '~> 3.5'
   spec.add_development_dependency 'rubocop', '~> 0.71'