[BURs] Don't use tag_string_diff for tag nuking

This doesn't have the same issue as mass updates, but
it doesn't hurt to change this away from tag_string_diff as well

Aliases/Implications still do this but considering this has been the case
for 4 years now I don't believe this to be a problem

app/jobs/tag_nuke_job.rb

@@ -28,7 +28,7 @@ class TagNukeJob < ApplicationJob
     Post.sql_raw_tag_match(tag_name).find_each do |post|
       post.with_lock do
         post.do_not_version_changes = true
-        post.tag_string_diff = "-#{tag_name}"
+        post.remove_tag(tag_name)
         post.save
       end
     end
@@ -50,7 +50,7 @@ class TagNukeJob < ApplicationJob
     TagRelUndo.where(tag_rel: tag, applied: false).find_each do |tag_rel_undo|
       Post.where(id: tag_rel_undo.undo_data).find_each do |post|
         post.do_not_version_changes = true
-        post.tag_string_diff = tag.name
+        post.add_tag(tag.name)
         post.save
       end
       tag_rel_undo.update(applied: true)

test/jobs/tag_nuke_job_test.rb

@@ -12,4 +12,13 @@ class TagNukeJobTest < ActiveJob::TestCase
     assert_equal("aa b c", p1.tag_string)
     assert_equal("dd y z", p2.tag_string)
   end
+
+  should "ignore aliases" do
+    CurrentUser.user = create(:user)
+    post = create(:post, tag_string: "extra new_tag")
+    create(:tag_alias, antecedent_name: "old_tag", consequent_name: "new_tag", status: "active")
+    TagNukeJob.perform_now("old_tag", CurrentUser.user.id)
+
+    assert_equal("extra new_tag", post.reload.tag_string)
+  end
 end