DEV: Update rubocop-discourse to latest version

The lastest version of rubocop-discourse enables rules regarding
plugins.

plugins/poll/lib/post_extension.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+module DiscoursePoll
+  module PostExtension
+    extend ActiveSupport::Concern
+
+    prepended do
+      attr_accessor :extracted_polls
+
+      has_many :polls, dependent: :destroy
+
+      after_save do
+        polls = self.extracted_polls
+        self.extracted_polls = nil
+        next if polls.blank? || !polls.is_a?(Hash)
+        post = self
+
+        ::Poll.transaction do
+          polls.values.each { |poll| DiscoursePoll::Poll.create!(post.id, poll) }
+          post.custom_fields[DiscoursePoll::HAS_POLLS] = true
+          post.save_custom_fields(true)
+        end
+      end
+    end
+  end
+end

plugins/poll/lib/user_extension.rb

@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+module DiscoursePoll
+  module UserExtension
+    extend ActiveSupport::Concern
+
+    prepended { has_many :poll_votes, dependent: :delete_all }
+  end
+end