Use RuboCop::Packaging amongst other extensions

And also fix the offenses shown by the respective cops.
The docs can be found here:
https://docs.rubocop.org/rubocop-packaging/cops_packaging.html

Signed-off-by: Utkarsh Gupta <utkarsh@debian.org>

.rubocop.yml

@@ -1,4 +1,5 @@
 require:
+  - rubocop-packaging
   - rubocop-performance
   - rubocop-rspec
 

paper_trail.gemspec

@@ -66,6 +66,7 @@ has been destroyed.
   s.add_development_dependency "rake", "~> 13.0"
   s.add_development_dependency "rspec-rails", "~> 4.0"
   s.add_development_dependency "rubocop", "~> 0.89.1"
+  s.add_development_dependency "rubocop-packaging", "~> 0.5.1"
   s.add_development_dependency "rubocop-performance", "~> 1.7.1"
   s.add_development_dependency "rubocop-rspec", "~> 1.42.0"
 

spec/generators/paper_trail/install_generator_spec.rb

@@ -2,7 +2,7 @@
 
 require "spec_helper"
 require "generator_spec/test_case"
-require File.expand_path("../../../lib/generators/paper_trail/install/install_generator", __dir__)
+require "generators/paper_trail/install/install_generator"
 
 RSpec.describe PaperTrail::InstallGenerator, type: :generator do
   include GeneratorSpec::TestCase