Update dependency grunt-contrib-uglify to v5

Author: renovate[bot]

assets/plugins/pace/package.json

@@ -15,7 +15,7 @@
   "devDependencies": {
     "grunt-contrib-coffee": "0.7.0",
     "coffee-script": "1.6.3",
-    "grunt-contrib-uglify": "0.2.7",
+    "grunt-contrib-uglify": "5.2.2",
     "grunt-cli": "0.1.13",
     "grunt": "0.4.5",
     "grunt-contrib-watch": "0.5.3",