[3.14] gh-135862: add C contiguous one-dimensional buffer requirement to `asyncio.StreamWriter` docs (GH-137910) (#137912)

gh-135862: add C contiguous one-dimensional buffer requirement to `asyncio.StreamWriter` docs (GH-137910)
(cherry picked from commit 1c3950abc1d403bddce5212c08d6c40e78486e9d)

Co-authored-by: Kumar Aditya <kumaraditya@python.org>