Rubocop: resolve Gemspec/DevelopmentDependencies

Gemfile

@@ -2,7 +2,14 @@
 
 source 'https://rubygems.org'
 
-git_source(:github) { |repo_name| "https://github.com/#{repo_name}" }
-
-# Specify your gem's dependencies in unwrappr.gemspec
 gemspec
+
+group :development do
+  gem 'guard', '~> 2'
+  gem 'guard-rspec', '~> 4'
+  gem 'pry', '~> 0'
+  gem 'rake', '>= 12.3.3'
+  gem 'rspec', '~> 3.0'
+  gem 'rspec-its', '~> 1'
+  gem 'rubocop', '>= 0.49.0'
+end

unwrappr.gemspec

@@ -45,14 +45,6 @@ Gem::Specification.new do |spec| # rubocop:disable Metrics/BlockLength:
   spec.add_dependency 'octokit', '~> 4.0'
   spec.add_dependency 'safe_shell', '~> 1'
 
-  spec.add_development_dependency 'guard', '~> 2'
-  spec.add_development_dependency 'guard-rspec', '~> 4'
-  spec.add_development_dependency 'pry', '~> 0'
-  spec.add_development_dependency 'rake', '>= 12.3.3'
-  spec.add_development_dependency 'rspec', '~> 3.0'
-  spec.add_development_dependency 'rspec-its', '~> 1'
-  spec.add_development_dependency 'rubocop', '>= 0.49.0'
-
   spec.metadata = {
     'bug_tracker_uri' => "#{GITHUB_URL}/issues",
     'changelog_uri' => "#{GITHUB_URL}/blob/HEAD/CHANGELOG.md",