[Deepspeed] non-native optimizers are mostly ok with zero-offload
As noticed in https://github.com/huggingface/transformers/issues/11044#issuecomment-870742459 most non-DS optimizers should work with zero-offload as long as they have cpu+gpu implementation (except LAMB).

So this PR relaxes the earlier incorrectly imposed restriction.

@sgugger 

