activitypub: use Object.delete() instead of mutating the database and cache directly

lib/pleroma/web/activity_pub/activity_pub.ex

@@ -273,8 +273,7 @@ def delete(%Object{data: %{"id" => id, "actor" => actor}} = object, local \\ tru
       "to" => [user.follower_address, "https://www.w3.org/ns/activitystreams#Public"]
     }
 
-    with Repo.delete(object),
-         Repo.delete_all(Activity.all_non_create_by_object_ap_id_q(id)),
+    with Object.delete(object),
          {:ok, activity} <- insert(data, local),
          :ok <- maybe_federate(activity),
          {:ok, _actor} <- User.decrease_note_count(user) do

lib/pleroma/web/common_api/common_api.ex

@@ -9,8 +9,7 @@ def delete(activity_id, user) do
     with %Activity{data: %{"object" => %{"id" => object_id}}} <- Repo.get(Activity, activity_id),
          %Object{} = object <- Object.normalize(object_id),
          true <- user.info["is_moderator"] || user.ap_id == object.data["actor"],
-         {:ok, delete} <- ActivityPub.delete(object),
-         {:ok, true} <- Cachex.del(:user_cache, "object:#{object_id}") do
+         {:ok, delete} <- ActivityPub.delete(object) do
       {:ok, delete}
     end
   end