Enable Style/RedundantParentheses rubocop cop

See #17478

.rubocop.yml

@@ -486,10 +486,9 @@ Style/RedundantException:
 Style/RedundantFreeze:
   Enabled: false
 
-# TODO: Enable RedundantParentheses Cop.
 # Checks for parentheses that seem not to serve any purpose.
 Style/RedundantParentheses:
-  Enabled: false
+  Enabled: true
 
 # Don't use return where it's not required.
 Style/RedundantReturn:

app/helpers/diff_helper.rb

@@ -39,11 +39,11 @@ module DiffHelper
   end
 
   def unfold_bottom_class(bottom)
-    (bottom) ? 'js-unfold-bottom' : ''
+    bottom ? 'js-unfold-bottom' : ''
   end
 
   def unfold_class(unfold)
-    (unfold) ? 'unfold js-unfold' : ''
+    unfold ? 'unfold js-unfold' : ''
   end
 
   def diff_line_content(line, line_type = nil)

config/initializers/session_store.rb

@@ -23,6 +23,6 @@ else
     secure: Gitlab.config.gitlab.https,
     httponly: true,
     expires_in: Settings.gitlab['session_expire_delay'] * 60,
-    path: (Rails.application.config.relative_url_root.nil?) ? '/' : Gitlab::Application.config.relative_url_root
+    path: Rails.application.config.relative_url_root.nil? ? '/' : Gitlab::Application.config.relative_url_root
   )
 end

lib/api/users.rb

@@ -76,7 +76,7 @@ module API
         required_attributes! [:email, :password, :name, :username]
         attrs = attributes_for_keys [:email, :name, :password, :skype, :linkedin, :twitter, :projects_limit, :username, :bio, :location, :can_create_group, :admin, :confirm, :external]
         admin = attrs.delete(:admin)
-        confirm = !(attrs.delete(:confirm) =~ (/(false|f|no|0)$/i))
+        confirm = !(attrs.delete(:confirm) =~ /(false|f|no|0)$/i)
         user = User.build_user(attrs)
         user.admin = admin unless admin.nil?
         user.skip_confirmation! unless confirm

spec/controllers/projects/merge_requests_controller_spec.rb

@@ -63,7 +63,7 @@ describe Projects::MergeRequestsController do
             id: merge_request.iid,
             format: format)
 
-        expect(response.body).to eq((merge_request.send(:"to_#{format}")).to_s)
+        expect(response.body).to eq(merge_request.send(:"to_#{format}").to_s)
       end
 
       it "should not escape Html" do