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:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

package-lock.json

@@ -12,7 +12,7 @@
     },
     "dependencies": {
         "gulp": "^5.0.0",
-        "gulp-autoprefixer": "^8.0.0",
+        "gulp-autoprefixer": "^9.0.0",
         "gulp-clean-css": "^4.3.0",
         "gulp-concat": "^2.6.1",
         "gulp-connect": "^5.7.0",