[issue31345] Backport docstring improvements to the C version of OrderedDict

[Roundup Robot]

Changes by Roundup Robot <devnull at psf.upfronthosting.co.za>:


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keywords: +patch
pull_requests: +3463
stage: needs patch -> patch review

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue31345>
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