user: filter out duplicate follow requests

lib/pleroma/user.ex

@@ -398,6 +398,7 @@ defmodule Pleroma.User do
       Enum.map(reqs, fn req -> req.actor end)
       |> Enum.uniq()
       |> Enum.map(fn ap_id -> get_by_ap_id(ap_id) end)
+      |> Enum.filter(fn u -> !following?(u, user) end)
 
     {:ok, users}
   end