chore(package): update postcss-sorting to version 1.6.1

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -63,7 +63,7 @@
     "postcss-initial": "^1.5.1",
     "postcss-mixins": "^4.0.2",
     "postcss-nested": "^1.0.0",
-    "postcss-sorting": "^1.6.0",
+    "postcss-sorting": "^1.6.1",
     "stylelint": "^6.7.1",
     "stylelint-config-standard": "^9.0.0",
     "updtr": "^0.2.0"