build: update dependency karma to v6 [security]

Author: renovate[bot]

package.json

@@ -109,7 +109,7 @@
     "jest": "24.9.0",
     "jest-preset-angular": "7.1.1",
     "json-schema-to-typescript": "^8.0.0",
-    "karma": "~4.4.0",
+    "karma": "~6.3.0",
     "karma-chrome-launcher": "~3.1.0",
     "karma-coverage-istanbul-reporter": "~2.1.0",
     "karma-jasmine": "~2.0.0",