Update sharp requirement from 0.21.1 to 0.21.3 (#4097)

Updates the requirements on [sharp](https://github.com/lovell/sharp) to permit the latest version.
- [Release notes](https://github.com/lovell/sharp/releases)
- [Changelog](https://github.com/lovell/sharp/blob/master/docs/changelog.md)
- [Commits](https://github.com/lovell/sharp/commits/v0.21.3

)

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