[3.3] Fixed concurrent issue of ClassGeneratorTest

[zrlw]

What is the purpose of the change?

https://github.com/apache/dubbo/actions/runs/13953617826/job/39059896642

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 60.79%. Comparing base (4ce9c6f) to head (f315100).
Report is 128 commits behind head on 3.3.

Additional details and impacted files

@@            Coverage Diff            @@
##                3.3   #15261   +/-   ##
=========================================
  Coverage     60.78%   60.79%           
+ Complexity    10896    10891    -5     
=========================================
  Files          1885     1885           
  Lines         86087    86087           
  Branches      12896    12896           
=========================================
+ Hits          52327    52334    +7     
  Misses        28312    28312           
+ Partials       5448     5441    -7     

Flag	Coverage Δ
integration-tests	33.13% <ø> (+0.01%)	⬆️
samples-tests	29.23% <ø> (+0.02%)	⬆️
unit-tests	58.92% <ø> (+0.01%)	⬆️

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