Added type hints for TFConvBertModel
Based on Issue #16059 

I have added type hints for the [TFConvBertModel](https://huggingface.co/docs/transformers/model_doc/convbert#transformers.TFConvBertModel).

@Rocketknight1 Could you kindly check if this is fine?

Thanks in advance.
_The documentation is not available anymore as the PR was closed or merged._<|||||>Thanks @Rocketknight1.