Bump degenerator and karma

Removes [degenerator](https://github.com/TooTallNate/node-degenerator). It's no longer used after updating ancestor dependency [karma](https://github.com/karma-runner/karma). These dependencies need to be updated together.


Removes `degenerator`

Updates `karma` from 2.0.0 to 6.4.1
- [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/v2.0.0...v6.4.1)

---
updated-dependencies:
- dependency-name: degenerator
  dependency-type: indirect
- dependency-name: karma
  dependency-type: direct:development
...

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

package.json

@@ -40,7 +40,7 @@
     "chai": "^4.1.2",
     "concat": "azer/concat",
     "concat-cli": "^4.0.0",
-    "karma": "^2.0.0",
+    "karma": "^6.4.1",
     "karma-chai": "^0.1.0",
     "karma-firefox-launcher": "^1.1.0",
     "karma-mocha": "^1.3.0",