Update bundler requirement from ~> 1.3 to ~> 2.0

Updates the requirements on [bundler](https://github.com/bundler/bundler) to permit the latest version.
- [Release notes](https://github.com/bundler/bundler/releases)
- [Changelog](https://github.com/bundler/bundler/blob/master/CHANGELOG.md)
- [Commits](rubygems/bundler@v1.3.0...v2.0.2)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

apt-spy2.gemspec

@@ -23,7 +23,7 @@ Gem::Specification.new do |spec|
   spec.add_dependency 'json'
   spec.add_dependency 'nokogiri', '>= 1.6', '< 1.11'
 
-  spec.add_development_dependency "bundler", "~> 1.3"
+  spec.add_development_dependency "bundler", "~> 2.0"
   spec.add_development_dependency "rake"
   spec.add_development_dependency "minitest", "~> 5.0.8"
   spec.add_development_dependency "coveralls"