revert: drop the alert feed widget, the notification center replaces it

plugins/alerts/locales/en.json

@@ -160,13 +160,5 @@
     "save": "Save",
     "saving": "Saving...",
     "delete": "Delete"
-  },
-  "widget": {
-    "name": "Alert Feed",
-    "description": "Your latest alerts, with a quick way to mark them read",
-    "maxItems": "Max items",
-    "showRead": "Show read alerts",
-    "allClear": "All clear",
-    "loading": "Loading..."
   }
 }