Revert "[TSP] last_norm allgather move to model.py"

[xiaoluomi]

Reverts #5911

[paddle-bot]

Thanks for your contribution!

[codecov-commenter]

Codecov Report

❌ Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (release/online/20251131@2e04b4e). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
fastdeploy/model_executor/models/gpt_oss.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@                    Coverage Diff                     @@
##             release/online/20251131    #5968   +/-   ##
==========================================================
  Coverage                           ?   57.49%           
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  Files                              ?      324           
  Lines                              ?    39350           
  Branches                           ?     5934           
==========================================================
  Hits                               ?    22624           
  Misses                             ?    14900           
  Partials                           ?     1826           

Flag	Coverage Δ
GPU	57.49% <66.66%> (?)

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