[3.3] Removed mGroup from NamedThreadFactory

[zrlw]

What is the purpose of the change?

try to fix #15201

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 60.74%. Comparing base (317bee1) to head (39fbbcf).
Report is 4 commits behind head on 3.3.

Additional details and impacted files

@@             Coverage Diff              @@
##                3.3   #15202      +/-   ##
============================================
- Coverage     60.75%   60.74%   -0.01%     
  Complexity    10885    10885              
============================================
  Files          1885     1885              
  Lines         86071    86068       -3     
  Branches      12892    12891       -1     
============================================
- Hits          52292    52283       -9     
- Misses        28325    28333       +8     
+ Partials       5454     5452       -2     

Flag	Coverage Δ
integration-tests	33.15% <100.00%> (+<0.01%)	⬆️
samples-tests	29.17% <100.00%> (-0.04%)	⬇️
unit-tests	58.91% <100.00%> (+0.01%)	⬆️

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