Remove deprecated Error::description

[AnderEnder]

Error::description has been documented as soft-deprecated since 1.27.0 (17 months ago). It is going to be hard-deprecated soon.

This PR:

• Removes an implementation of Error::description

Related PR: rust-lang/rust#66919

[KodrAus]

Thanks! This looks good to me

[BurntSushi]

Hmm, removing this is a breaking change I think. Was that intentional? (Although it's probably a pretty minor breaking change.)

[LukasKalbertodt]

Does anyone know what the minimum Rust version of this crate was (before this PR)?

For error-chain we went with a solution that conditionally has the description method to avoid bumping the minimum required Rust version (final PR, previous PR with discussion).

[KodrAus]

Ah I assumed because we didn’t have a MSRV already, and because getopts is typically an app rather than library dependency, that we just weren’t tracking one and bumps to the Rust version were ok 🙂 That could have been a bad assumption to make.