Bump structopt from 0.3.20 to 0.3.21
Bump structopt from 0.3.20 to 0.3.21

Bumps [structopt](https://github.com/TeXitoi/structopt) from 0.3.20 to 0.3.21.
- [Release notes](https://github.com/TeXitoi/structopt/releases)
- [Changelog](https://github.com/TeXitoi/structopt/blob/master/CHANGELOG.md)
- [Commits](https://github.com/TeXitoi/structopt/compare/v0.3.20...v0.3.21)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
dalance/gip