remove getAttributeMap of ServiceMetada

[Jeff-Lv]

What is the purpose of the change

remove getAttributeMap of ServiceMetada

Brief changelog

XXXXX

Verifying this change

XXXXX

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[codecov-io]

Codecov Report

Merging #3542 into 3.x-dev will decrease coverage by 0.07%.
The diff coverage is 0%.

@@              Coverage Diff              @@
##             3.x-dev    #3542      +/-   ##
=============================================
- Coverage      63.81%   63.74%   -0.08%     
  Complexity        75       75              
=============================================
  Files            655      655              
  Lines          28422    28422              
  Branches        4808     4808              
=============================================
- Hits           18137    18117      -20     
- Misses          8008     8023      +15     
- Partials        2277     2282       +5

Impacted Files	Coverage Δ	Complexity Δ
...va/org/apache/dubbo/rpc/model/ServiceMetadata.java	58.33% <0%> (ø)	0 <0> (ø)	⬇️
.../apache/dubbo/remoting/transport/AbstractPeer.java	58.69% <0%> (-10.87%)	0% <0%> (ø)
...che/dubbo/remoting/transport/mina/MinaChannel.java	43.42% <0%> (-10.53%)	0% <0%> (ø)
...e/dubbo/remoting/transport/netty/NettyChannel.java	56.47% <0%> (-5.89%)	0% <0%> (ø)
...he/dubbo/remoting/transport/netty/NettyServer.java	67.85% <0%> (-3.58%)	0% <0%> (ø)
...dubbo/remoting/exchange/support/DefaultFuture.java	71.14% <0%> (-2.02%)	0% <0%> (ø)
...pache/dubbo/remoting/transport/AbstractServer.java	47.91% <0%> (-1.05%)	0% <0%> (ø)
...pache/dubbo/registry/support/AbstractRegistry.java	81.2% <0%> (-0.76%)	0% <0%> (ø)
...bbo/registry/support/ProviderConsumerRegTable.java	85.36% <0%> (+4.87%)	0% <0%> (ø)	⬇️
...in/java/org/apache/dubbo/common/utils/JVMUtil.java	81.13% <0%> (+7.54%)	0% <0%> (ø)	⬇️

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