Tests: Remove unneeded explicit cachex use.

Only use cachex when we're actually testing it.

test/pleroma/web/plugs/cache_test.exs

@@ -3,7 +3,7 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 defmodule Pleroma.Web.Plugs.CacheTest do
-  use ExUnit.Case, async: true
+  use Pleroma.DataCase
   use Plug.Test
 
   alias Pleroma.Web.Plugs.Cache
@@ -24,11 +24,6 @@ defmodule Pleroma.Web.Plugs.CacheTest do
 
   @ttl 5
 
-  setup do
-    Cachex.clear(:web_resp_cache)
-    :ok
-  end
-
   test "caches a response" do
     assert @miss_resp ==
              conn(:get, "/")