tests: fix unit tests.

* Move old post archive tests to post version tests.

* Fix pool tests that assumed that multiple edits by the same user
  weren't merged.

* Fix references to `is_active` and `notes` on artist model.

test/unit/d_text_test.rb

@@ -93,7 +93,7 @@ class DTextTest < ActiveSupport::TestCase
 
       should "not link general tags to artist pages" do
         tag = create(:tag, name: "cat")
-        artist = create(:artist, name: "cat", is_active: false)
+        artist = create(:artist, name: "cat", is_deleted: true)
 
         assert_match(%r!/wiki_pages/cat!, DText.format_text("[[cat]]"))
       end