Ruby 3.0 support, drop support for Ruby < 2.4

telegram-bot.gemspec

@@ -17,7 +17,7 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ['lib']
 
-  spec.required_ruby_version = '~> 2.0'
+  spec.required_ruby_version = '>= 2.4'
 
   spec.add_dependency 'actionpack', '>= 4.0', '< 6.2'
   spec.add_dependency 'activesupport', '>= 4.0', '< 6.2'