Update netty4_version to 4.2.12.Final

[RainYuY]

What is the purpose of the change?

Checklist

• Make sure there is a GitHub_issue field for the change.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Write necessary unit-test to verify your logic correction. If the new feature or significant change is committed, please remember to add sample in dubbo samples project.
• Make sure gitHub actions can pass. Why the workflow is failing and how to fix it?

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.78%. Comparing base (69084bd) to head (f6e6fdb).

Additional details and impacted files

@@             Coverage Diff              @@
##                3.3   #16196      +/-   ##
============================================
- Coverage     60.80%   58.78%   -2.03%     
+ Complexity    11756       15   -11741     
============================================
  Files          1953     1953              
  Lines         89118    89119       +1     
  Branches      13444    13445       +1     
============================================
- Hits          54188    52387    -1801     
- Misses        29368    31035    +1667     
- Partials       5562     5697     +135     

Flag	Coverage Δ
integration-tests-java21	?
integration-tests-java8	?
samples-tests-java21	?
samples-tests-java8	?
unit-tests-java11	59.01% <100.00%> (-0.03%)	⬇️
unit-tests-java17	58.51% <100.00%> (-0.01%)	⬇️
unit-tests-java21	58.50% <100.00%> (-0.02%)	⬇️
unit-tests-java25	58.45% <100.00%> (-0.01%)	⬇️
unit-tests-java8	59.05% <100.00%> (+0.02%)	⬆️

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