Rollup merge of #70760 - PonasKovas:docs, r=Dylan-DPC

docs: make the description of Result::map_or more clear

The documentation of [`Result::map_or`](https://doc.rust-lang.org/std/result/enum.Result.html#method.map_or) is very unclear and confusing, probably because it was copied straight from [`Option::map_or`](https://doc.rust-lang.org/std/option/enum.Option.html#method.map_or) and someone forgot to adapt it for Result.