The vivi.c driver has long gone, but v4l2-videobuf.rst still
refers to it. Just drop that reference since it is no longer valid
or relevant (videobuf is deprecated).

The QUERYCAP documentation also made a reference to is, but there
vivi could just be replaced by vivid, the vivi successor.
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>