refactor: remove unused audio component/endpoint

Nothing seems to be calling this endpoint in production, and the only
reference to it in the code is this `Audio` component, which itself is
not imported anywhere.

Since this was the only case where we sent Polly requests using plain
text instead of SSML, the parameter for text type can also be removed.

lib/screens/audio.ex

@@ -20,11 +20,11 @@ defmodule Screens.Audio do
 
   @type departure_group :: {departure_group_key(), [map()]}
 
-  @spec synthesize(String.t(), String.t(), keyword()) :: {:ok, binary()} | :error
-  def synthesize(ssml_string, text_type, log_meta) do
+  @spec synthesize(String.t(), keyword()) :: {:ok, binary()} | :error
+  def synthesize(ssml_string, log_meta) do
     result =
       ssml_string
-      |> ExAws.Polly.synthesize_speech(lexicon_names: @lexicon_names, text_type: text_type)
+      |> ExAws.Polly.synthesize_speech(lexicon_names: @lexicon_names, text_type: "ssml")
       |> ExAws.request()
 
     case result do

lib/screens_web/controllers/audio_controller.ex

@@ -38,7 +38,7 @@ defmodule ScreensWeb.AudioController do
          template_assigns <- Screens.Audio.from_api_data(data, screen_id),
          ssml <- render_ssml(template_assigns),
          {:ok, audio_data} <-
-           Screens.Audio.synthesize(ssml, "ssml", screen_id: screen_id, is_screen: is_screen) do
+           Screens.Audio.synthesize(ssml, screen_id: screen_id, is_screen: is_screen) do
       send_audio(conn, {:binary, audio_data}, disposition)
     else
       _ -> send_fallback_audio(conn, is_screen, screen_id, disposition)

lib/screens_web/controllers/v2/audio_controller.ex

@@ -47,20 +47,10 @@ defmodule ScreensWeb.V2.AudioController do
     end
   end
 
-  def text_to_speech(conn, %{"text" => text}) do
-    case Screens.Audio.synthesize(text, "text", is_screen: false) do
-      {:ok, audio_data} ->
-        send_download(conn, {:binary, audio_data}, filename: "readout.mp3", disposition: :inline)
-
-      :error ->
-        not_found(conn)
-    end
-  end
-
   defp readout(conn, screen_id, real_screen?, disposition) do
     screen_id
     |> fetch_ssml()
-    |> Screens.Audio.synthesize("ssml", screen_id: screen_id, is_screen: real_screen?)
+    |> Screens.Audio.synthesize(screen_id: screen_id, is_screen: real_screen?)
     |> case do
       {:ok, audio_data} ->
         send_download(conn, {:binary, audio_data},

lib/screens_web/router.ex

@@ -123,12 +123,8 @@ defmodule ScreensWeb.Router do
       pipe_through [:redirect_prod_http, :browser, :api]
 
       get "/:id/readout.mp3", AudioController, :show
-
       get "/:id/volume", AudioController, :show_volume
-
       get "/:id/debug", AudioController, :debug
-
-      get "/text_to_speech/:text", AudioController, :text_to_speech
     end
   end