Remove jasmine ruby gem and its requiring

This was missed from the pull request that
replaced the jasmine ruby gem with the
jasmine-browser-runner:

#382

Author: tombye

Rakefile

@@ -1,6 +1,5 @@
 require "bundler/gem_tasks"
 require "rspec/core/rake_task"
-require "jasmine"
 
 RSpec::Core::RakeTask.new(:spec)
 

govuk_tech_docs.gemspec

@@ -57,7 +57,6 @@ Gem::Specification.new do |spec|
 
   spec.add_development_dependency "byebug"
   spec.add_development_dependency "capybara", "~> 3.32"
-  spec.add_development_dependency "jasmine", "~> 3.5"
   spec.add_development_dependency "rake", "~> 13.0"
   spec.add_development_dependency "rspec", "~> 3.9"
   spec.add_development_dependency "rubocop-govuk", "~> 4.10"