migrations: drop filler migration

priv/repo/migrations/20180829082743_fill_recipients_to_and_cc_fields_in_activities.exs

-defmodule Pleroma.Repo.Migrations.FillRecipientsToAndCcFieldsInActivities do
-  use Ecto.Migration
-  alias Pleroma.{Repo, Activity}
-
-  def up do
-    max = Repo.aggregate(Activity, :max, :id)
-    if max do
-      IO.puts("#{max} activities")
-      chunks = 0..(round(max / 10_000))
-
-      Enum.each(chunks, fn (i) ->
-        min = i * 10_000
-        max = min + 10_000
-        execute("""
-        update activities set recipients_to = array(select jsonb_array_elements_text(data->'to')) where id > #{min} and id <= #{max} and jsonb_typeof(data->'to') = 'array';
-        """)
-        |> IO.inspect
-        execute("""
-        update activities set recipients_cc = array(select jsonb_array_elements_text(data->'cc')) where id > #{min} and id <= #{max} and jsonb_typeof(data->'cc') = 'array';
-        """)
-        |> IO.inspect
-      end)
-    end
-  end
-end