Include sidekiq_middleware in coverage report

spec/simplecov_env.rb

@@ -52,7 +52,6 @@ module SimpleCovEnv
       add_filter '/app/controllers/sherlock/' # Profiling tool used only in development
       add_filter '/bin/'
       add_filter 'db/fixtures/' # Matches EE files as well
-      add_filter '/lib/gitlab/sidekiq_middleware/'
 
       add_group 'Channels',     'app/channels' # Matches EE files as well
       add_group 'Controllers',  'app/controllers' # Matches EE files as well