remove _get_pretty_exception_message from PrestoHook

[jeffolsi]

What happened:

There is no actual need for _get_pretty_exception_message this Hook is the only hook of DBs that is trying to wrap the exception raised from the db itself.
Airflow needs to be consistent either do this for all hooks or don't do it at all.
There is no reason to do this for Presto but not for Postgresql or Mysql
https://github.com/apache/airflow/blob/v1-10-stable/airflow/hooks/presto_hook.py#L74