ArticleNotePageValidator: fix replies fixing

Some software, like GoToSocial, expose replies as ActivityPub
Collections, but do not expose any item array directly in the object,
causing validation to fail via the ObjectID validator. Now, Pleroma will
drop that field in this situation too.

test/pleroma/web/activity_pub/object_validators/article_note_page_validator_test.exs

@@ -54,4 +54,17 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.ArticleNotePageValidatorTest
 
     %{valid?: true} = ArticleNotePageValidator.cast_and_validate(note)
   end
+
+  test "a Note without replies/first/items validates" do
+    insert(:user, ap_id: "https://mastodon.social/users/emelie")
+
+    note =
+      "test/fixtures/tesla_mock/status.emelie.json"
+      |> File.read!()
+      |> Jason.decode!()
+      |> pop_in(["replies", "first", "items"])
+      |> elem(1)
+
+    %{valid?: true} = ArticleNotePageValidator.cast_and_validate(note)
+  end
 end