Avoid name conflict between parser gem and our AR model

The module name `Parser` of the `parser` gem, that is a dependency from
rubocop, will clash with our `Parser` AR model. This can be avoided by
not requiring rubocop in the Gemfile which means it's code and
dependencies do not get loaded in the rails server process.

Gemfile

@@ -63,8 +63,8 @@ group :development do
   gem 'spring'
   gem 'spring-commands-rspec'
 
-  gem 'rubocop', '~> 0.58.1'
-  gem 'rubocop-rspec', '~> 1.29'
+  gem 'rubocop', '~> 0.58.1', require: false
+  gem 'rubocop-rspec', '~> 1.29', require: false
 end
 
 group :development, :test do