Rollup merge of #126191 - ivan-shrimp:nonzero_doc, r=scottmcm

Fix `NonZero` doctest inconsistencies

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`NonZero`'s doctests contain both `?` and `.unwrap()` with no obvious reason for the difference, so this changes all of them to `?`. Also removes an explicit `std::num::NonZero`.

Author: matthiaskrgr