fix(@schematics/angular): update karma to version 4

Fixes #13724

Author: Alan Agius

packages/schematics/angular/workspace/files/package.json.template

@@ -34,7 +34,7 @@
     "codelyzer": "~4.5.0",
     "jasmine-core": "~2.99.1",
     "jasmine-spec-reporter": "~4.2.1",
-    "karma": "~3.1.1",
+    "karma": "~4.0.0",
     "karma-chrome-launcher": "~2.2.0",
     "karma-coverage-istanbul-reporter": "~2.0.1",
     "karma-jasmine": "~1.1.2",