media: staging: rkisp1: remove TODO item to document quantization handling

The quantization handling is already documented
in the file rkisp1.rst so this item can be removed.

Fixes: 66167269 (media: staging: rkisp1: allow quantization setting by userspace on the isp source pad)
Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>