Update Bundler version

Author: afrase

zerobounce.gemspec

@@ -29,7 +29,7 @@ Gem::Specification.new do |spec| # rubocop:disable Metrics/BlockLength
   spec.add_dependency 'faraday', '>= 0.14', '< 2.0'
   spec.add_dependency 'faraday_middleware', '~> 1.0'
 
-  spec.add_development_dependency 'bundler', '~> 2.1.4'
+  spec.add_development_dependency 'bundler', '~> 2.2.17'
   spec.add_development_dependency 'pry', '~> 0.14.1'
   spec.add_development_dependency 'rake', '~> 13.0'
   spec.add_development_dependency 'rspec', '~> 3.0'