Fix new credo warnings

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

lib/service/export/participants/csv.ex

@@ -41,7 +41,7 @@ defmodule Mobilizon.Service.Export.Participants.CSV do
                |> Repo.stream()
                |> Stream.map(&to_list/1)
                |> NimbleCSV.RFC4180.dump_to_iodata()
-               |> (fn stream -> Stream.concat([Enum.join(columns(), ","), "\n"], stream) end).()
+               |> add_header_column()
                |> Stream.each(fn line -> IO.write(file, line) end)
                |> Stream.run()
 
@@ -63,6 +63,10 @@ defmodule Mobilizon.Service.Export.Participants.CSV do
     end
   end
 
+  defp add_header_column(stream) do
+    Stream.concat([Enum.join(columns(), ","), "\n"], stream)
+  end
+
   @spec save_csv_upload(String.t(), String.t(), Event.t()) ::
           {:ok, Export.t()} | {:error, atom() | Ecto.Changeset.t()}
   defp save_csv_upload(full_path, filename, %Event{id: event_id, title: title}) do