Remove unused schema.

lib/runosaari/core/performer_performance.ex

@@ -1,18 +0,0 @@
-defmodule Runosaari.Core.PerformerPerformance do
-  use Ecto.Schema
-  import Ecto.Changeset
-
-  schema "performer_performance" do
-    field :performer_id, :id
-    field :performance_id, :id
-
-    timestamps()
-  end
-
-  @doc false
-  def changeset(performer_performance, attrs) do
-    performer_performance
-    |> cast(attrs, [])
-    |> validate_required([])
-  end
-end