Bump gulp-autoprefixer from 6.1.0 to 8.0.0

Bumps [gulp-autoprefixer](https://github.com/sindresorhus/gulp-autoprefixer) from 6.1.0 to 8.0.0.
- [Release notes](https://github.com/sindresorhus/gulp-autoprefixer/releases)
- [Commits](sindresorhus/gulp-autoprefixer@v6.1.0...v8.0.0)

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

Author: dependabot-preview[bot]

package.json

@@ -28,7 +28,7 @@
     "fancy-log": "^1.3.3",
     "gulp": "^4.0.2",
     "gulp-accessibility": "^3.1.1",
-    "gulp-autoprefixer": "^6.1.0",
+    "gulp-autoprefixer": "^8.0.0",
     "gulp-babel": "^8.0.0",
     "gulp-compile-handlebars": "^0.6.1",
     "gulp-concat": "^2.6.1",