Fix `TFRemBertModelTest.test_resize_token_embeddings`
# What does this PR do?

Fix `TFRemBertModelTest.test_resize_token_embeddings`.

This method

https://github.com/huggingface/transformers/blob/028d4b7c8be2c2fc1146fcc1e9bd253c1a7ea346/src/transformers/modeling_tf_utils.py#L1449

assumes that `word_embedding_weight` has the same shape as `old_lm_head_decoder`, but this is not the case for `TFRemBertModel`, as it has `input_embedding_size` and `output_embedding_size` in config.

This PR checks the shape before checking the values. If shape is not equal, it means the input/output are not equal.

Fix the CI failure [here](https://github.com/huggingface/transformers/runs/6682139350?check_suite_focus=true)
A quick look on 
https://github.com/huggingface/transformers/blob/028d4b7c8be2c2fc1146fcc1e9bd253c1a7ea346/src/transformers/modeling_utils.py#L1315

~~I couldn't find equivalent logic about `is_input_output_equals` that was in TF.~~

Guess it is because we use `self.config.tie_word_embeddings` to check in PyTorch.<|||||>> # What does this PR do?
> Fix `TFRemBertModelTest.test_resize_token_embeddings`.
> 
> This method
> 
> https://github.com/huggingface/transformers/blob/028d4b7c8be2c2fc1146fcc1e9bd253c1a7ea346/src/transformers/modeling_tf_utils.py#L1449
> 
> assumes that `word_embedding_weight` has the same shape as `old_lm_head_decoder`, but this is not the case for `TFRemBertModel`, as it has `input_embedding_size` and `output_embedding_size` in config.
> 
> This PR checks the shape before checking the values. If shape is not equal, it means the input/output are not equal.
> 
> Fix the CI failure [here](https://github.com/huggingface/transformers/runs/6682139350?check_suite_focus=true)

Sounds like an exception to me! I'm not super well versed in TF word embeddings. Think we don't have the prettiest logic there... 

@Rocketknight1 @gante what would you suggest here? 

Also cc @sgugger <|||||>I confess I don't know much about TF word embeddings, so I'll have to dive deeper to review.

There is one thing I know, though -- it uses TF1 code, and it is on my update list 😅   <|||||>The embeddings in TF are using very very dark magic. I would refrain from any change in `modeling_tf_utils` (so let RemBERT fail for now) until it has been cleaned up by the TF team :-)<|||||>OK, so I will close this PR today without merge, if everyone is OK<|||||>@ydshieh it'd be great if you could open an issue (update TF embeddings) and link this closed PR to it<|||||>Closed for now with this issue #17540 opened.