media: uAPI: buffer.rst: remove a left-over documentation

Changeset 129134e5 ("media: media/v4l2: remove V4L2_FLAG_MEMORY_NON_CONSISTENT flag")
reverted an uAPI flag, but it kept some left-overs at the documentation.

Drop them too. This should solve this warning:

	Documentation/userspace-api/media/v4l/buffer.rst:692: WARNING: The "flat-table" directive is empty; content required.

	.. flat-table::
	    :header-rows:  0
	    :stub-columns: 0
	    :widths:       3 1 4

Fixes: 129134e5

 ("media: media/v4l2: remove V4L2_FLAG_MEMORY_NON_CONSISTENT flag")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>