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[bot] <support@github.com>

package.json

@@ -44,7 +44,7 @@
     "@babel/core": "^7.13.8",
     "@storybook/addon-a11y": "^6.1.21",
     "@storybook/addon-actions": "^6.1.21",
-    "@storybook/addon-essentials": "^6.1.18",
+    "@storybook/addon-essentials": "^6.1.21",
     "@storybook/addon-info": "^5.3.21",
     "@storybook/addon-jest": "^6.1.21",
     "@storybook/addon-knobs": "^6.1.21",