Remove obsolete changeset/2 function from projection version schema

lib/projections/ecto.ex

@@ -51,7 +51,6 @@ defmodule Commanded.Projections.Ecto do
       use Ecto.Schema
       use Commanded.Event.Handler, @handler_opts
 
-      import Ecto.Changeset
       import Ecto.Query
       import unquote(__MODULE__)
 
@@ -205,24 +204,15 @@ defmodule Commanded.Projections.Ecto do
     quote do
       defmodule ProjectionVersion do
         @moduledoc false
-
         use Ecto.Schema
 
-        import Ecto.Changeset
-
         @primary_key {:projection_name, :string, []}
 
         schema "projection_versions" do
           field(:last_seen_event_number, :integer)
 
           timestamps(type: :naive_datetime_usec)
         end
-
-        @required_fields ~w(last_seen_event_number)a
-
-        def changeset(model, params \\ :invalid) do
-          cast(model, params, @required_fields)
-        end
       end
     end
   end