Bump toml from 0.5.6 to 0.5.8

Bumps [toml](https://github.com/alexcrichton/toml-rs) from 0.5.6 to 0.5.8.
- [Release notes](https://github.com/alexcrichton/toml-rs/releases)
- [Commits](toml-rs/toml-rs@0.5.6...0.5.8)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]