Re CLC #293 - Don't specify Data.List.NonEmpty in terms of partial

See https://github.com/haskell/core-libraries-committee/issues/293

`List.init` had already been driven out of `tails1` by 21fc180b but this specification also avoided partial `fromList`, so I preferred it.

The `changelog.md` for `base` is updated, with an entry added under `base-4.22.0.0`.