[Security] Bump http from 0.1.18 to 0.1.21
[Security] Bump http from 0.1.18 to 0.1.21

Bumps [http](https://github.com/hyperium/http) from 0.1.18 to 0.1.21. **This update includes security fixes.**
- [Release notes](https://github.com/hyperium/http/releases)
- [Changelog](https://github.com/hyperium/http/blob/v0.1.21/CHANGELOG.md)
- [Commits](https://github.com/hyperium/http/compare/v0.1.18...v0.1.21)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
jasonwhite/button-rs