Remove files that are not used in the project

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

.rubocop.yml

@@ -2,17 +2,9 @@
 AllCops:
   Exclude:
     - 'spec/**/*'
-    - 'features/**/*'
     - 'vendor/**/*'
-    - 'db/**/*'
     - 'tmp/**/*'
     - 'bin/**/*'
-    - 'lib/backup/**/*'
-    - 'lib/tasks/**/*'
-    - 'lib/email_validator.rb'
-    - 'lib/gitlab/upgrader.rb'
-    - 'lib/gitlab/seeder.rb'
-    - 'lib/vendor/**/*'
     - 'hooks/**/*'
     - 'Guardfile'