Revert "Document handle_info/2 (elixir-ecto#317)"

This reverts commit 4776530.

Author: ruslandoga

lib/db_connection.ex

@@ -362,15 +362,6 @@ defmodule DBConnection do
   """
   @callback disconnect(err :: Exception.t(), state :: any) :: :ok
 
-  @doc """
-  Optional callback for handling messages received by the connection.
-
-  Returns `{:disconnect, exception}` to close the connection or `:ok` to continue.
-  """
-  @callback handle_info(message :: any, state :: any) :: {:disconnect, Exception.t()} | :ok
-
-  @optional_callbacks handle_info: 2
-
   @connection_module_key :connection_module
 
   @doc """