Tests: Remove unneeded explicit cachex use.

Only use cachex when we're actually testing it.

test/pleroma/web/media_proxy/invalidation/http_test.exs

@@ -9,10 +9,6 @@ defmodule Pleroma.Web.MediaProxy.Invalidation.HttpTest do
   import ExUnit.CaptureLog
   import Tesla.Mock
 
-  setup do
-    on_exit(fn -> Cachex.clear(:banned_urls_cache) end)
-  end
-
   test "logs hasn't error message when request is valid" do
     mock(fn
       %{method: :purge, url: "http://example.com/media/example.jpg"} ->

test/pleroma/web/media_proxy/invalidation/script_test.exs

@@ -8,10 +8,6 @@ defmodule Pleroma.Web.MediaProxy.Invalidation.ScriptTest do
 
   import ExUnit.CaptureLog
 
-  setup do
-    on_exit(fn -> Cachex.clear(:banned_urls_cache) end)
-  end
-
   test "it logger error when script not found" do
     assert capture_log(fn ->
              assert Invalidation.Script.purge(