Update readme

[kun-song]

What is the purpose of the change

Correct some typos.

Brief changelog

XXXXX

Verifying this change

XXXXX

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[codecov-io]

Codecov Report

Merging #2488 into master will decrease coverage by 0.02%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #2488      +/-   ##
============================================
- Coverage     55.03%   55.01%   -0.03%     
+ Complexity     5268     5267       -1     
============================================
  Files           573      573              
  Lines         25454    25454              
  Branches       4520     4520              
============================================
- Hits          14009    14003       -6     
- Misses         9350     9355       +5     
- Partials       2095     2096       +1

Impacted Files	Coverage Δ	Complexity Δ
...onfig/spring/extension/SpringExtensionFactory.java	75% <0%> (-10.72%)	10% <0%> (ø)
.../dubbo/remoting/transport/netty4/NettyChannel.java	57.5% <0%> (-8.75%)	21% <0%> (-2%)
...ubbo/rpc/protocol/dubbo/ChannelWrappedInvoker.java	41.66% <0%> (-4.17%)	3% <0%> (ø)
...e/dubbo/remoting/transport/netty4/NettyServer.java	72.13% <0%> (-3.28%)	9% <0%> (-1%)
.../src/main/java/org/apache/dubbo/rpc/RpcStatus.java	57.89% <0%> (-1.06%)	18% <0%> (ø)
...pache/dubbo/registry/support/AbstractRegistry.java	69.28% <0%> (+0.74%)	63% <0%> (+1%)	⬆️
...apache/dubbo/rpc/protocol/dubbo/FutureAdapter.java	64.51% <0%> (+6.45%)	3% <0%> (ø)	⬇️
...he/dubbo/remoting/transport/netty/NettyClient.java	81.35% <0%> (+8.47%)	13% <0%> (+1%)	⬆️

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[diecui1202]

looks good to me.