Add missing newline to NEWS entry

[hugovk]

Follow on from #31046.

After merge, the CI complained about a missing newline:

Starting: Build documentation
==============================================================================
Task         : Command line
Description  : Run a command line script using Bash on Linux and macOS and cmd.exe on Windows
Version      : 2.200.2
Author       : Microsoft Corporation
Help         : https://docs.microsoft.com/azure/devops/pipelines/tasks/utility/command-line
==============================================================================
Generating script.
Script contents:
make check html PYTHON=python
========================== Starting Command Output ===========================
/usr/bin/bash --noprofile --norc /home/vsts/work/_temp/87ee4e78-ecff-4ef4-908d-8f9026f9e23a.sh
PATH=./venv/bin:$PATH sphinx-lint -i tools -i ./venv -i README.rst
No problems found.
PATH=./venv/bin:$PATH sphinx-lint ../Misc/NEWS.d/next/
[1] ../Misc/NEWS.d/next/Core and Builtins/2022-02-01-10-05-27.[bpo-43721](https://bugs.python.org/issue43721).-1XAIo.rst:0: No newline at end of file (no-newline-at-end-of-file).
1 problem with severity 1 found.
make: *** [Makefile:219: check] Error 1
##[error]Bash exited with code '2'.
Finishing: Build documentation

https://dev.azure.com/Python/cpython/_build/results?buildId=98584&view=logs&j=4db1505a-29e5-5cc0-240b-53a8a2681f75&t=a975920c-8356-5388-147c-613d5fab0171

(To run locally: make -C Doc check html PYTHON=python)

[miss-islington]

Thanks @hugovk for the PR, and @iritkatriel for merging it 🌮🎉.. I'm working now to backport this PR to: 3.9.
🐍🍒⛏🤖

[miss-islington]

Thanks @hugovk for the PR, and @iritkatriel for merging it 🌮🎉.. I'm working now to backport this PR to: 3.10.
🐍🍒⛏🤖

[bedevere-bot]

GH-31894 is a backport of this pull request to the 3.9 branch.

[bedevere-bot]

GH-31896 is a backport of this pull request to the 3.10 branch.