BURs: remove ability to skip secondary validations.

Remove the ability to skip secondary validations when creating a BUR.
The only skippable validation that still existed was the requirement
that both tags in an implication must have wiki pages. It's now
mandatory to write wiki pages for tags before you can request an
implication. This doesn't apply to empty tags.

app/models/bulk_update_request.rb

@@ -1,7 +1,6 @@
 class BulkUpdateRequest < ApplicationRecord
   attr_accessor :title
   attr_accessor :reason
-  attr_reader :skip_secondary_validations
 
   belongs_to :user
   belongs_to :forum_topic, optional: true
@@ -75,7 +74,7 @@ class BulkUpdateRequest < ApplicationRecord
       transaction do
         CurrentUser.scoped(approver) do
           processor.process!(approver)
-          update!(status: "approved", approver: approver, skip_secondary_validations: true)
+          update!(status: "approved", approver: approver)
           forum_updater.update("The #{bulk_update_request_link} (forum ##{forum_post.id}) has been approved by @#{approver.name}.")
         end
       end
@@ -120,10 +119,6 @@ class BulkUpdateRequest < ApplicationRecord
     self.tags = processor.affected_tags
   end
 
-  def skip_secondary_validations=(v)
-    @skip_secondary_validations = v.to_s.truthy?
-  end
-
   def processor
     @processor ||= BulkUpdateRequestProcessor.new(self)
   end