gh-36609: avoid using `itertools.pairwise`
Method `pairwise` has been introduced in `itertools` version 3.10. As
reported in #36493, its use breaks the condo workflow with Python 3.9.
So we modify the code to avoid using `pairwise`.
### :memo: Checklist
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### :hourglass: Dependencies
See discussion
https://github.com/sagemath/sage/pull/36493#issuecomment-1786350920,
URL: https://github.com/sagemath/sage/pull/36609
Reported by: David Coudert
Reviewer(s): Tobias Diez
