Assert message error in Reformer chunking
# 🐛 Bug

In the function `apply_chunking_to_forward`, an assertion checking the input tensor shape is trying to print the contents of the tensor itself instead of its shape:

https://github.com/huggingface/transformers/blob/b5015a2a0f4ea63035a877f5626cb0c3ce97e25d/src/transformers/modeling_utils.py#L2195

I'm pretty sure that line should be `input_tensors[0].shape[chunk_dim], chunk_size`