add table support flag for prometheus

public/app/plugins/datasource/prometheus/plugin.json

@@ -23,6 +23,7 @@
   "alerting": true,
   "annotations": true,
   "explore": true,
+  "tables": true,
   "queryOptions": {
     "minInterval": true
   },
@@ -44,4 +45,4 @@
     ],
     "version": "5.0.0"
   }
-}
+}