Bump gulp-autoprefixer from 8.0.0 to 9.0.0

Bumps [gulp-autoprefixer](https://github.com/sindresorhus/gulp-autoprefixer) from 8.0.0 to 9.0.0.
- [Release notes](https://github.com/sindresorhus/gulp-autoprefixer/releases)
- [Commits](sindresorhus/gulp-autoprefixer@v8.0.0...v9.0.0)

---
updated-dependencies:
- dependency-name: gulp-autoprefixer
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

package.json

@@ -41,7 +41,7 @@
     "eslint-import-resolver-webpack": "^0.13.0",
     "eslint-plugin-import": "^2.7.0",
     "gulp": "^4.0.0",
-    "gulp-autoprefixer": "^8.0.0",
+    "gulp-autoprefixer": "^9.0.0",
     "gulp-clean-css": "^4.0.0",
     "gulp-dart-sass": "^1.0.2",
     "gulp-eslint-new": "^1.6.0",