Add error message to Wav2Vec2 & Hubert if labels > vocab_size
# 🚀 Feature request

Add better error message to `HubertForCTC`, `Wav2Vec2ForCTC` if labels are bigger than vocab size.

## Motivation

Following this issue: https://github.com/huggingface/transformers/issues/12264 it is clear that an error message should be thrown if any of the any of the labels are > `self.config.vocab_size` or else silent errors can sneak into the training script.

So we should modify: `Wav2Vec2ForCTC`, `TFWav2Vec2ForCTC`, and `HubertForCTC` to add a nice error message in this case.

## Your contribution

This is a first good issue and should be rather easy to accomplish. I'm happy to give more guidance if needed.

I will create a PR to fix this.<|||||>@vasudevgupta7 @patrickvonplaten Is this fixed? If not, I will like to work on it. <|||||>Hey, this issue has been fixed in this PR: https://github.com/huggingface/transformers/pull/12288<|||||>Thanks for informing. I had seen it, but since the issue is still open, I thought something might be left. <|||||>Closing as fixed :)