Update sinon requirement in /packages/generator/app/templates

Updates the requirements on [sinon](https://github.com/sinonjs/sinon) to permit the latest version.
- [Release notes](https://github.com/sinonjs/sinon/releases)
- [Changelog](https://github.com/sinonjs/sinon/blob/master/CHANGELOG.md)
- [Commits](sinonjs/sinon@v7.3.2...v7.4.1)

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

packages/generator/app/templates/package.json

@@ -66,7 +66,7 @@
     "karma-webpack": "^4.0.2",
     "mocha": "^6.2.0",
     "react-test-renderer": "^16.8.6",
-    "sinon": "^7.3.2",
+    "sinon": "^7.4.1",
     "sinon-chai": "^3.3.0",
     "stylelint": "^10.1.0",
     "xvfb-maybe": "^0.2.1",