Stringify truncated function data in Logger (#4562)

Signed-off-by: José Valim <jose.valim@plataformatec.com.br>

Author: amorphid

lib/logger/lib/logger.ex

@@ -562,7 +562,7 @@ defmodule Logger do
   end
 
   defp truncate(data, n) when is_function(data, 0),
-    do: Logger.Utils.truncate(data.(), n)
+    do: truncate(data.(), n)
   defp truncate(data, n) when is_list(data) or is_binary(data),
     do: Logger.Utils.truncate(data, n)
   defp truncate(data, n),