Tests: Reset all cachex caches between synchronous tests

Don't bother in the async case, it doesn't make sense there.

test/support/conn_case.ex

@@ -116,12 +116,11 @@ defmodule Pleroma.Web.ConnCase do
   end
 
   setup tags do
-    Cachex.clear(:user_cache)
-    Cachex.clear(:object_cache)
     :ok = Ecto.Adapters.SQL.Sandbox.checkout(Pleroma.Repo)
 
     unless tags[:async] do
       Ecto.Adapters.SQL.Sandbox.mode(Pleroma.Repo, {:shared, self()})
+      Pleroma.DataCase.clear_cachex()
     end
 
     if tags[:needs_streamer] do