Remove authors from Cargo metadata (per RFC 3052)

[xtqqczze]

The authors field has been deprecated since rust-lang/cargo#15068.

[sylvestre]

error: failed to parse manifest at `/home/runner/work/coreutils/coreutils/Cargo.toml`

Caused by:
  error inheriting `authors` from workspace root manifest's `workspace.package.authors`

Caused by:
  `workspace.package.authors` was not defined

[cakebaker]

Thanks!