Update karma to 4.2.0

Also update karma-chrome-launcher, karma-coverage-istanbul-reporter,
and karma-webpack.
Signed-off-by: NTakuya Noguchi <takninnovationresearch@gmail.com>

changelogs/unreleased/65660-update-karma-to-4-2-0.yml

+---
+title: Update karma to 4.2.0
+merge_request: 31495
+author: Takuya Noguchi
+type: other

package.json

@@ -176,14 +176,14 @@
     "jest-util": "^24.0.0",
     "jsdoc": "^3.5.5",
     "jsdoc-vue": "^1.0.0",
-    "karma": "^3.0.0",
-    "karma-chrome-launcher": "^2.2.0",
-    "karma-coverage-istanbul-reporter": "^2.0.4",
+    "karma": "^4.2.0",
+    "karma-chrome-launcher": "^3.0.0",
+    "karma-coverage-istanbul-reporter": "^2.1.0",
     "karma-jasmine": "^1.1.2",
     "karma-junit-reporter": "^1.2.0",
     "karma-mocha-reporter": "^2.2.5",
     "karma-sourcemap-loader": "^0.3.7",
-    "karma-webpack": "^4.0.0-beta.0",
+    "karma-webpack": "^4.0.2",
     "md5": "^2.2.1",
     "node-sass": "^4.12.0",
     "nodemon": "^1.18.9",