message: Dubbo docs - Fix statistics root value
  Update the dubbo doc to specify the statistics root as `dubbo.` instead of `redis.`
  (https://github.com/envoyproxy/envoy/blob/5248a4fb7d4c2a3d1fa151f944d3a63f6b7a06cf/source/extensions/filters/network/dubbo_proxy/config.cc#L101)
diff: @@ -17,7 +17,7 @@ and parameter value for routing.
  Statistics
  ----------
  -Every configured dubbo proxy filter has statistics rooted at *redis.<stat_prefix>.* with the
  +Every configured dubbo proxy filter has statistics rooted at *dubbo.<stat_prefix>.* with the
  following statistics:
  .. csv-table::
  