Bump gulp-autoprefixer from 7.0.1 to 8.0.0

Bumps [gulp-autoprefixer](https://github.com/sindresorhus/gulp-autoprefixer) from 7.0.1 to 8.0.0.
- [Release notes](https://github.com/sindresorhus/gulp-autoprefixer/releases)
- [Commits](https://github.com/sindresorhus/gulp-autoprefixer/compare/v7.0.1...v8.0.0)

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

package.json

@@ -33,7 +33,7 @@
   "devDependencies": {
     "browser-sync": "^2.26.7",
     "gulp": "^4.0.2",
-    "gulp-autoprefixer": "^7.0.1",
+    "gulp-autoprefixer": "^8.0.0",
     "gulp-concat": "^2.6.1",
     "gulp-rename": "^2.0.0",
     "gulp-ruby-sass": "^4.0.0",