chore(deps): update dependency bundler to v2 [security]

Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

git-contributors.gemspec

@@ -18,7 +18,7 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ["lib"]
 
-  spec.add_development_dependency "bundler", "~> 1.5"
+  spec.add_development_dependency "bundler", "~> 2.2", ">= 2.2.33"
   spec.add_development_dependency "rake", "~> 10"
 
   spec.add_dependency 'diffy', '~> 3.0'