Update testing matrix

gemfiles/rails_42.gemfile

@@ -1,21 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "actionpack", "~> 4.2.0"
-gem "railties", "~> 4.2.0"
-
-group :development do
-  gem "appraisal", "~> 2.2"
-  gem "pry", "~> 0.14.1"
-  gem "pry-byebug", "~> 3.10.1"
-  gem "sdoc", "~> 2.0.3"
-  gem "telegram-bot-types", "~> 0.6.3"
-  gem "rspec", "~> 3.12.0"
-  gem "rspec-its", "~> 1.3.0"
-  gem "rspec-rails", "~> 4.0.2"
-  gem "rubocop", "~> 0.52.1"
-  gem "coveralls", "~> 0.8.23", require: false
-end
-
-gemspec path: "../"

gemfiles/rails_50.gemfile

@@ -1,21 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "actionpack", "~> 5.0.0"
-gem "railties", "~> 5.0.0"
-
-group :development do
-  gem "appraisal", "~> 2.2"
-  gem "pry", "~> 0.14.1"
-  gem "pry-byebug", "~> 3.10.1"
-  gem "sdoc", "~> 2.0.3"
-  gem "telegram-bot-types", "~> 0.6.3"
-  gem "rspec", "~> 3.12.0"
-  gem "rspec-its", "~> 1.3.0"
-  gem "rspec-rails", "~> 4.0.2"
-  gem "rubocop", "~> 0.52.1"
-  gem "coveralls", "~> 0.8.23", require: false
-end
-
-gemspec path: "../"