chore: update dev-dependencies

Signed-off-by: Miroslav Bajtoš <mbajtoss@gmail.com>

Gruntfile.js

@@ -3,8 +3,8 @@
 // This file is licensed under the MIT License.
 // License text available at https://opensource.org/licenses/MIT
 
-/* global module:false */
 'use strict';
+
 module.exports = function(grunt) {
   // Do not report warnings from unit-tests exercising deprecated paths
   process.env.NO_DEPRECATION = 'loopback';

package.json

@@ -75,15 +75,15 @@
     "grunt": "^1.0.1",
     "grunt-browserify": "^5.0.0",
     "grunt-cli": "^1.2.0",
-    "grunt-contrib-uglify": "^3.4.0",
+    "grunt-contrib-uglify": "^4.0.1",
     "grunt-contrib-watch": "^1.0.0",
-    "grunt-eslint": "^21.0.0",
+    "grunt-eslint": "^22.0.0",
     "grunt-karma": "^3.0.2",
     "grunt-mocha-test": "^0.13.3",
     "is-docker": "^2.0.0",
     "karma": "^4.1.0",
     "karma-browserify": "^6.0.0",
-    "karma-chrome-launcher": "^2.2.0",
+    "karma-chrome-launcher": "^3.1.0",
     "karma-es6-shim": "^1.0.0",
     "karma-firefox-launcher": "^1.0.0",
     "karma-html2js-preprocessor": "^1.0.0",
@@ -92,14 +92,14 @@
     "karma-script-launcher": "^1.0.0",
     "loopback-boot": "^2.7.0",
     "loopback-context": "^1.0.0",
-    "mocha": "^5.2.0",
+    "mocha": "^6.2.1",
     "nyc": "^14.1.1",
-    "sinon": "^6.1.4",
+    "sinon": "^7.5.0",
     "sinon-chai": "^3.2.0",
     "strong-error-handler": "^3.0.0",
     "strong-task-emitter": "^0.0.8",
-    "supertest": "^3.0.0",
-    "which": "^1.3.1"
+    "supertest": "^4.0.2",
+    "which": "^2.0.1"
   },
   "repository": {
     "type": "git",