Bump gulp-autoprefixer from 5.0.0 to 6.1.0 in /arctic/static/arctic (#…

…364)

Bumps [gulp-autoprefixer](https://github.com/sindresorhus/gulp-autoprefixer) from 5.0.0 to 6.1.0.
- [Release notes](https://github.com/sindresorhus/gulp-autoprefixer/releases)
- [Commits](sindresorhus/gulp-autoprefixer@v5.0.0...v6.1.0)

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

arctic/static/arctic/package.json

@@ -32,7 +32,7 @@
     "babel-preset-es2015": "^6.24.1",
     "babel-register": "^6.26.0",
     "gulp": "^4.0.0",
-    "gulp-autoprefixer": "^5.0.0",
+    "gulp-autoprefixer": "^6.1.0",
     "gulp-babel": "^7.0.1",
     "gulp-cli": "^2.1.0",
     "gulp-concat": "^2.6.1",