media: pixfmt-compressed.rst: fix 'bullet' formatting

Drop the 'bullets' for the HEVC stateless codec documentation.
It doesn't work, and they just show up as asterisks.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>