[3.3] Optimized EagerThreadPoolExecutorTest by decreasing maximumPoolSize

[zrlw]

What is the purpose of the change?

try to fix #15204

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 (3771339) to head (8fcd1cc).

Additional details and impacted files

@@             Coverage Diff              @@
##                3.3   #15205      +/-   ##
============================================
+ Coverage     60.78%   60.79%   +0.01%     
- Complexity    10888    10889       +1     
============================================
  Files          1885     1885              
  Lines         86071    86071              
  Branches      12892    12892              
============================================
+ Hits          52315    52324       +9     
+ Misses        28308    28303       -5     
+ Partials       5448     5444       -4     

Flag	Coverage Δ
integration-tests	33.14% <ø> (+<0.01%)	⬆️
samples-tests	29.20% <ø> (+0.02%)	⬆️
unit-tests	58.92% <ø> (+<0.01%)	⬆️

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