Fix most rubocop issues (#2165)

* Run rubocop --autocorrect on app/, config/ and lib/, also manually fix some remaining style issues

* Run rubocop --autocorrect-all on db/

* Run rubocop --autocorrect-all on `spec/` and fix remaining issues

app/serializers/rest/status_serializer.rb

@@ -13,7 +13,7 @@ class REST::StatusSerializer < ActiveModel::Serializer
   attribute :muted, if: :current_user?
   attribute :bookmarked, if: :current_user?
   attribute :pinned, if: :pinnable?
-  attribute :local_only if :local?
+  attribute :local_only, if: :local?
   has_many :filtered, serializer: REST::FilterResultSerializer, if: :current_user?
 
   attribute :content, unless: :source_requested?
@@ -32,6 +32,8 @@ class REST::StatusSerializer < ActiveModel::Serializer
   has_one :preview_card, key: :card, serializer: REST::PreviewCardSerializer
   has_one :preloadable_poll, key: :poll, serializer: REST::PollSerializer
 
+  delegate :local?, to: :object
+
   def id
     object.id.to_s
   end