SMPLify betas initialization not align with 'use_one_betas_per_video'

[Wei-Chen-hub]

In this case:

1. setting use_one_betas_per_video=True
2. initializing SMPLify with a changing betas sequence init_betas=betas_sequence # (100,10)

Betas for all frames would have the same gardiant update during SMPLify iterations, therefore the final output is still a varying betas sequence. Maybe can add a warning or an average process for betas?