[issue42396] Add a whatsnew entry about async contextlib.nullcontext

[miss-islington]

New submission from miss-islington <mariatta.wijaya+miss-islington at gmail.com>:


New changeset 9c98e8cc3ebf56d01183c67adbc000ed19b8e0f4 by Tom Gringauz in branch 'master':
bpo-42396: Add a whatsnew entry about async contextlib.nullcontext (GH-23357)
https://github.com/python/cpython/commit/9c98e8cc3ebf56d01183c67adbc000ed19b8e0f4


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nosy: +miss-islington

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue42396>
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