Bump grunt-webpack from 3.1.3 to 4.0.2

Bumps [grunt-webpack](https://github.com/webpack-contrib/grunt-webpack) from 3.1.3 to 4.0.2.
- [Release notes](https://github.com/webpack-contrib/grunt-webpack/releases)
- [Commits](webpack-contrib/grunt-webpack@v3.1.3...v4.0.2)

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

package.json

@@ -45,7 +45,7 @@
     "grunt-karma": "^3.0.2",
     "grunt-karma-coveralls": "^2.5.4",
     "grunt-run": "^0.8.1",
-    "grunt-webpack": "^3.1.3",
+    "grunt-webpack": "^4.0.2",
     "jest": "^26.1.0",
     "karma": "^4.4.1",
     "karma-chrome-launcher": "^3.1.0",