Fix incorrect descriptions for dubbo-serialization module.

[carryxyh]

Fix incorrect descriptions for dubbo-serialization module.
Simple fix which doesn't need test.

[carryxyh]

Will bring back to 2.6.x.

[codecov-io]

Codecov Report

Merging #2620 into master will increase coverage by 0.02%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #2620      +/-   ##
============================================
+ Coverage     55.04%   55.07%   +0.02%     
  Complexity     5286     5286              
============================================
  Files           571      571              
  Lines         25521    25521              
  Branches       4530     4530              
============================================
+ Hits          14048    14055       +7     
+ Misses         9364     9356       -8     
- Partials       2109     2110       +1

Impacted Files	Coverage Δ	Complexity Δ
...onfig/spring/extension/SpringExtensionFactory.java	68.96% <0%> (-6.9%)	11% <0%> (ø)
...he/dubbo/registry/multicast/MulticastRegistry.java	55.6% <0%> (-1.73%)	35% <0%> (-3%)
...ache/dubbo/remoting/transport/mina/MinaClient.java	56.92% <0%> (-1.54%)	8% <0%> (-1%)
.../java/org/apache/dubbo/config/ReferenceConfig.java	51.07% <0%> (+0.71%)	42% <0%> (ø)	⬇️
...rpc/protocol/dubbo/telnet/InvokeTelnetHandler.java	57.83% <0%> (+3.61%)	15% <0%> (+2%)	⬆️
...che/dubbo/remoting/transport/mina/MinaChannel.java	54.92% <0%> (+12.67%)	17% <0%> (+2%)	⬆️

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