Merge pull request #554 from textpattern/greenkeeper/autoprefixer-9.7.4

Update autoprefixer to the latest version 🚀

Author: philwareham

package.json

@@ -25,7 +25,7 @@
     "url": "https://github.com/textpattern/textpattern-default-theme/issues"
   },
   "devDependencies": {
-    "autoprefixer": "9.7.3",
+    "autoprefixer": "9.7.4",
     "clean-webpack-plugin": "3.0.0",
     "copy-webpack-plugin": "5.1.1",
     "cross-env": "6.0.3",