transmission: add ftruncate syscall to seccomp

Fixes many crashes.

Fixes #22071.

Signed-off-by: Marius Dinu <m95d+git@psihoexpert.ro>
(cherry picked from commit a0372545887a2f16329be56949465e13af0d04c7)
Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>