remove this after process group destroy supported

[todo]

bagua/tests/contrib/test_fused_optimizer.py

Lines 132 to 137 in 5add7f8

     # TODO: remove this after process group destroy supported 
     if not bagua.communication.is_initialized(): 
         bagua.init_process_group() 
  
  
 def run(opt, flag_param, device, num_epochs): 

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This issue was generated by todo based on a TODO comment in 5add7f8 when #207 was merged. cc @BaguaSys.