Build(deps-dev): bump gatsby-plugin-styled-components (#6417)

Bumps [gatsby-plugin-styled-components](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-plugin-styled-components) from 4.2.0 to 4.3.0.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-plugin-styled-components/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/gatsby-plugin-styled-components@4.3.0/packages/gatsby-plugin-styled-components)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>
Co-authored-by: repo-ranger[bot] <39074581+repo-ranger[bot]@users.noreply.github.com>

package.json

@@ -194,7 +194,7 @@
     "gatsby-plugin-page-creator": "^3.3.0",
     "gatsby-plugin-react-helmet": "^4.1.0",
     "gatsby-plugin-remove-trailing-slashes": "^3.1.0",
-    "gatsby-plugin-styled-components": "^4.2.0",
+    "gatsby-plugin-styled-components": "^4.3.0",
     "gatsby-plugin-typescript": "^3.2.0",
     "humanize-string": "^2.1.0",
     "husky": "^4.3.8",