BURs: credit tag edits to DanbooruBot.

Credit tag edits that are performed as part of an alias, implication, or
mass update to DanbooruBot instead of the admin who approved the BUR.

app/models/bulk_update_request.rb

@@ -77,7 +77,7 @@ class BulkUpdateRequest < ApplicationRecord
       transaction do
         CurrentUser.scoped(approver) do
           AliasAndImplicationImporter.new(script, forum_topic_id, "1", true).process!
-          update(status: "approved", approver: CurrentUser.user, skip_secondary_validations: true)
+          update!(status: "approved", approver: approver, skip_secondary_validations: true)
           forum_updater.update("The #{bulk_update_request_link} (forum ##{forum_post.id}) has been approved by @#{approver.name}.", "APPROVED")
         end
       end