build(deps): bump error-chain from 0.12.3 to 0.12.4
Bumps [error-chain](https://github.com/rust-lang-nursery/error-chain) from 0.12.3 to 0.12.4. - [Release notes](https://github.com/rust-lang-nursery/error-chain/releases) - [Changelog](https://github.com/rust-lang-nursery/error-chain/blob/master/CHANGELOG.md) - [Commits](rust-lang-nursery/error-chain@0.12.3...0.12.4) Signed-off-by: dependabot-preview[bot] <support@dependabot.com>
