Make all tests async

Doesn't make a difference at this stage, but it's a good foundation as
the application grows.

test/music_library_web/controllers/cover_controller_test.exs

@@ -1,5 +1,5 @@
 defmodule MusicLibraryWeb.CoverControllerTest do
-  use MusicLibraryWeb.ConnCase
+  use MusicLibraryWeb.ConnCase, async: true
 
   import MusicLibrary.RecordsFixtures
 

test/music_library_web/controllers/stats_controller_test.exs

@@ -1,5 +1,5 @@
 defmodule MusicLibraryWeb.StatsControllerTest do
-  use MusicLibraryWeb.ConnCase
+  use MusicLibraryWeb.ConnCase, async: true
 
   alias MusicLibrary.Records.Record
 

test/music_library_web/live/record_index_test.exs

@@ -1,5 +1,5 @@
 defmodule MusicLibraryWeb.RecordIndexTest do
-  use MusicLibraryWeb.ConnCase
+  use MusicLibraryWeb.ConnCase, async: true
 
   import Phoenix.LiveViewTest
   import MusicLibrary.RecordsFixtures

test/music_library_web/live/record_show_test.exs

@@ -1,5 +1,5 @@
 defmodule MusicLibraryWeb.RecordShowTest do
-  use MusicLibraryWeb.ConnCase
+  use MusicLibraryWeb.ConnCase, async: true
 
   import Phoenix.LiveViewTest
   import MusicLibrary.RecordsFixtures