po: Update Portuguese Translation.

Cherry-picked from 2.4 branch of commit:
a14f73a1921e6cd002a58ff8a5ba3d39129729f3

This commit log (with no ChangeLog entry) is written by gniibe,
following the practice; Translation update don't need a ChangeLog
entry in a commit log.

• Signed-off-by: Daniel Cerqueira <dan.git@brilhante.top>