build(deps): bump rlua from 0.19.7 to 0.19.8

Bumps [rlua](https://github.com/amethyst/rlua) from 0.19.7 to 0.19.8.
- [Changelog](https://github.com/amethyst/rlua/blob/master/CHANGELOG.md)
- [Commits](mlua-rs/rlua@v0.19.7...v0.19.8)

---
updated-dependencies:
- dependency-name: rlua
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>