Fix dialyzer error for "bad record mac" handling

The error was:

    lib/myxql/connection.ex:344:call
    The function call will not succeed.

    :ssl.format_error({:error, {:tls_alert, [32 | 97 | 98 | 99 | 100 | 101 | 109 | 111 | 114, ...]}})

    will never return since it differs in arguments with
    positions 1st from the success typing arguments:

    (
      atom()
      | maybe_improper_list()
      | {:error,
         atom()
         | maybe_improper_list()
         | {:error,
            atom()
            | maybe_improper_list()
            | {:error, atom() | maybe_improper_list() | {_, _}}
            | {:options, _}
            | {:tls_alert, {_, _}}}
         | {:options, _}
         | {:tls_alert, {_, _}}}
      | {:options, _}
      | {:tls_alert, {_, _}}
    )

lib/myxql/connection.ex

@@ -337,7 +337,7 @@ defmodule MyXQL.Connection do
   defp format_reason(:timeout), do: "timeout"
   defp format_reason(:closed), do: "socket closed"
 
-  defp format_reason({:tls_alert, 'bad record mac'} = reason) do
+  defp format_reason({:tls_alert, {:bad_record_mac, _}} = reason) do
     versions = :ssl.versions()[:supported]
 
     """