Update dependency karma to v6 [SECURITY]

Author: renovate[bot]

package.json

@@ -70,7 +70,7 @@
         "grunt-mocha-test": "^0.13.3",
         "grunt-scss-lint": "^0.5.0",
         "istanbul": "^0.4.5",
-        "karma": "^3.0.0",
+        "karma": "^6.0.0",
         "karma-chrome-launcher": "^2.2.0",
         "karma-mocha": "^1.3.0",
         "karma-ng-html2js-preprocessor": "~1.0.0",