Merge pull request #8781 from mozilla/greenkeeper/less-3.5.3

Update less to the latest version 🚀

package.json

@@ -21,7 +21,7 @@
     "jquery-pjax": "2.0.1",
     "jquery-ui": "1.12.1",
     "jszip": "3.1.4",
-    "less": "3.5.2",
+    "less": "3.5.3",
     "source-map": "0.7.3",
     "raven-js": "3.26.3",
     "timeago": "1.6.2",