Bump karma from 4.1.0 to 4.2.0 in /js

Bumps [karma](https://github.com/karma-runner/karma) from 4.1.0 to 4.2.0.
- [Release notes](https://github.com/karma-runner/karma/releases)
- [Changelog](https://github.com/karma-runner/karma/blob/master/CHANGELOG.md)
- [Commits](https://github.com/karma-runner/karma/compare/v4.1.0...v4.2.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

js/package.json

@@ -32,7 +32,7 @@
     "@babel/preset-env": "^7.4.5",
     "babel-loader": "^8.0.6",
     "css-loader": "^3.0.0",
-    "karma": "^4.1.0",
+    "karma": "^4.2.0",
     "mini-css-extract-plugin": "^0.7.0",
     "style-loader": "^0.23.1",
     "uglifyjs-webpack-plugin": "^2.1.3",