feat(@angular-devkit/build-angular): drop support for karma version 5.2

BREAKING CHANGE:

Minimum supported `karma` version is `6.0.0`

Author: alan-agius4

packages/angular_devkit/build_angular/package.json

@@ -82,7 +82,7 @@
     "@angular/compiler-cli": "^11.0.0 || ^11.2.0-next",
     "@angular/localize": "^11.0.0 || ^11.2.0-next",
     "@angular/service-worker": "^11.0.0 || ^11.2.0-next",
-    "karma": "^5.2.0 || ^6.0.0",
+    "karma": "^6.0.0",
     "ng-packagr": "^11.0.0 || ^11.2.0-next",
     "protractor": "^7.0.0",
     "tailwindcss": "^2.0.0",