BURs: don't log mod actions for aliases/implications/mass updates.

Don't log mod actions when aliases, implications, or mass updates are
processed.

Originally aliases and implications were logged because they could be
approved outside of a BUR. Mass updates could also be performed by mods
without making a forum request. This is no longer the case.

They were also logged for debugging purposes. This is no longer needed.
This generated a lot of spam in the mod action logs when a large BUR was
approved.

test/jobs/tag_batch_change_job_test.rb

@@ -11,10 +11,5 @@ class TagBatchChangeJobTest < ActiveJob::TestCase
       TagBatchChangeJob.perform_now("aaa", "bbb")
       assert_equal("bbb", @post.reload.tag_string)
     end
-
-    should "log a modaction" do
-      TagBatchChangeJob.perform_now("1", "2")
-      assert_equal("mass_update", ModAction.last.category)
-    end
   end
 end