Bump autoprefixer from 9.8.0 to 9.8.4

Bumps [autoprefixer](https://github.com/postcss/autoprefixer) from 9.8.0 to 9.8.4.
- [Release notes](https://github.com/postcss/autoprefixer/releases)
- [Changelog](https://github.com/postcss/autoprefixer/blob/master/CHANGELOG.md)
- [Commits](postcss/autoprefixer@9.8.0...9.8.4)

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

package.json

@@ -88,7 +88,7 @@
     "@storybook/addons": "5.3.19",
     "@storybook/react": "5.3.19",
     "@storybook/source-loader": "5.3.19",
-    "autoprefixer": "9.8.0",
+    "autoprefixer": "9.8.4",
     "babel-eslint": "11.0.0-beta.2",
     "babel-jest": "26.0.1",
     "babel-loader": "8.1.0",