media: vivid.rst: fix TV and S-Video Inputs section

remove the double word 'in'.

Signed-off-by: Deming Wang <wangdeming@inspur.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>