chore(deps-dev): bump @storybook/addon-essentials from 6.1.20 to 6.1.21

Bumps [@storybook/addon-essentials](https://github.com/storybookjs/storybook/tree/HEAD/addons/essentials) from 6.1.20 to 6.1.21.
- [Release notes](https://github.com/storybookjs/storybook/releases)
- [Changelog](https://github.com/storybookjs/storybook/blob/next/CHANGELOG.md)
- [Commits](https://github.com/storybookjs/storybook/commits/v6.1.21/addons/essentials)

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

Author: dependabot-preview[bot]