Tests: Make as many tests as possible async.

In general, tests that match these criteria can be made async:

- Doesn't use real Cachex.
- Doesn't write to the Config / Application Environment.
- Uses Mock. Using Mox is fine.
- Uses the streamer.

test/pleroma/web/uploader_controller_test.exs

@@ -3,7 +3,7 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 defmodule Pleroma.Web.UploaderControllerTest do
-  use Pleroma.Web.ConnCase
+  use Pleroma.Web.ConnCase, async: true
   alias Pleroma.Uploaders.Uploader
 
   describe "callback/2" do