Remove obsolete HACK comment

lib/last_fm/feed.ex

@@ -28,8 +28,6 @@ defmodule LastFm.Feed do
       |> Enum.map(fn t -> Map.take(t, @insertable_fields) end)
       |> Enum.map(&Map.to_list/1)
 
-    # HACK: if two tracks happen to have the exact same scrobbled_at_uts,
-    # we move it by a sec.
     MusicLibrary.Repo.insert_all(LastFm.Track, track_params,
       on_conflict: :nothing,
       conflict_target: [:scrobbled_at_uts, :title]