Simplify Rakefile

This didn't need the extra complexity, which was unconventional - and
this repo doesn't even have an integration folder under spec 🤔.

Rakefile

@@ -1,24 +1,9 @@
-require "bundler/setup"
 require "bundler/gem_tasks"
-
-Bundler::GemHelper.install_tasks
-
 require "rspec/core/rake_task"
-desc "Run all specs"
-RSpec::Core::RakeTask.new(:spec) do |task|
-  task.pattern = "spec/**/*_spec.rb"
-end
+require "rubocop/rake_task"
 
-namespace :spec do
-  desc "Run integration specs"
-  RSpec::Core::RakeTask.new(:integration) do |task|
-    task.pattern = "spec/integration/**/*_spec.rb"
-  end
-end
-
-desc "Lint Ruby"
-task :lint do
-  sh "bundle exec rubocop --format clang"
-end
+Bundler::GemHelper.install_tasks
+RSpec::Core::RakeTask.new(:spec)
+RuboCop::RakeTask.new
 
-task default: %i[spec lint]
+task default: %i[rubocop spec]