Remove Documentation/pt_BR/gittutorial.txt

This file is rather outdated and IMHO shouldn't be there in the first place.
(If there are translations of the Git documentation they are better be kept
separate from the original documentation.)

Signed-off-by: Thomas Ackermann <th.acker@arcor.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: tacker66