Remove requirement for `authors` field

Hey,

Currently the authors field in your Cargo.toml is required. (I am not sure if that's in general or this has something to do with wix?).

This field is deprecated.

Maybe move this into the dist.toml and that's gets used as a fallback.

Start by locating where cargo-dist validates the authors field in Cargo.toml and how dist.toml is loaded. Check whether the Wix-related behavior is involved and whether dist.toml already supports author metadata. Done means Cargo.toml no longer requires this deprecated field and the proposed dist.toml fallback behavior is covered by relevant tests.

Written by the indexing model from the issue text.