gh-89253: Add 3.10 whatsnew section for itertools.pairwise (GH-91563)

GH-89253

[`pairwise()`](https://docs.python.org/3/library/itertools.htmlGH-itertools.pairwise) already has the 'new in python3.10'

Automerge-Triggered-By: GH:rhettinger
(cherry picked from commit 5dcfb916c765d825b2e8372281d71d32316b41cf)

Co-authored-by: slateny <46876382+slateny@users.noreply.github.com>