downgrade karma-coverage-istanbul-reporter

Author: Feiyang1

package.json

@@ -108,7 +108,7 @@
     "karma": "5.1.0",
     "karma-chrome-launcher": "3.1.0",
     "karma-cli": "2.0.0",
-    "karma-coverage-istanbul-reporter": "3.0.3",
+    "karma-coverage-istanbul-reporter": "2.1.1",
     "karma-firefox-launcher": "1.3.0",
     "karma-mocha": "2.0.1",
     "karma-safari-launcher": "1.0.0",