Correctly update vocab size in resize_token_embeddings with pad_to_multiple_of!=0
Author: zrqiao
Pull request: yes

# What does this PR do?

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In [PreTrainedModel.resize_token_embeddings](https://github.com/huggingface/transformers/blob/0a55d9f7376f72ad3ff296d4249840021b03bcc4/src/transformers/modeling_utils.py#L1068), the vocabulary size attributes are not correctly updated if `pad_to_multiple_of!=None`. This led to tensor size mismatches in CausalLM loss calculation.

This PR implements a hotfix for this issue. 

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Comments:
Hey ! I think the patch release should have brought the fix! 

> Hey ! I think the patch release should have bought the fix!

Thanks!!