polish code

[chenlushun]

What is the purpose of the change

polish code

Brief changelog

incubator-dubbo/dubbo-registry/dubbo-registry-zookeeper/pom.xml
org.apache.dubbo.registry.zookeeper.ZookeeperRegistry

Verifying this change

XXXXX

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[codecov-io]

Codecov Report

Merging #3820 into master will increase coverage by 0.05%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##             master   #3820      +/-   ##
===========================================
+ Coverage     63.54%   63.6%   +0.05%     
  Complexity       71      71              
===========================================
  Files           704     704              
  Lines         31065   31065              
  Branches       5037    5037              
===========================================
+ Hits          19741   19759      +18     
+ Misses         9050    9034      -16     
+ Partials       2274    2272       -2

Impacted Files	Coverage Δ	Complexity Δ
...he/dubbo/registry/zookeeper/ZookeeperRegistry.java	67.37% <100%> (ø)	0 <0> (ø)	⬇️
...che/dubbo/remoting/transport/mina/MinaChannel.java	43.42% <0%> (-10.53%)	0% <0%> (ø)
...he/dubbo/remoting/transport/netty/NettyServer.java	69.64% <0%> (-3.58%)	0% <0%> (ø)
.../exchange/support/header/HeaderExchangeServer.java	66.98% <0%> (-0.95%)	0% <0%> (ø)
.../apache/dubbo/remoting/transport/AbstractPeer.java	63.04% <0%> (ø)	0% <0%> (ø)	⬇️
...dubbo/remoting/exchange/support/DefaultFuture.java	73.46% <0%> (ø)	0% <0%> (ø)	⬇️
...he/dubbo/registry/multicast/MulticastRegistry.java	69.68% <0%> (+1.8%)	0% <0%> (ø)	⬇️
...exchange/support/header/HeaderExchangeHandler.java	62.2% <0%> (+2.36%)	0% <0%> (ø)	⬇️
...bo/rpc/cluster/support/FailbackClusterInvoker.java	70.49% <0%> (+3.27%)	0% <0%> (ø)	⬇️
...e/dubbo/remoting/transport/netty/NettyChannel.java	62.35% <0%> (+4.7%)	0% <0%> (ø)	⬇️
... and 5 more

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[kezhenxu94]

LGTM