TAPAS tokenizer is unable to handle indexed dataframes
Running the following code will result in a `iloc` error:

```python
from transformers import TapasTokenizer
import pandas as pd

model_name = 'google/tapas-base'
tokenizer = TapasTokenizer.from_pretrained(model_name)

data = {'Actors': ["Brad Pitt", "Leonardo Di Caprio", "George Clooney"], 'Number of movies': ["87", "53", "69"]}
queries = ["What is the name of the first actor?", "How many movies has George Clooney played in?", "What is the total number of movies?"]
answer_coordinates = [[(0, 0)], [(2, 1)], [(0, 1), (1, 1), (2, 1)]]
answer_text = [["Brad Pitt"], ["69"], ["209"]]
table = pd.DataFrame.from_dict(data)

# Let's add random years - this will break the tokenzier
table.index = [2000, 2010, 2020]

inputs = tokenizer(table=table, queries=queries, answer_coordinates=answer_coordinates, answer_text=answer_text, padding='max_length', return_tensors='pt')
inputs
```
Hi,

This has been reported before in #10265. Would you mind opening a PR to fix this?<|||||>@NielsRogge I started a PR here: https://github.com/huggingface/transformers/pull/14549

I'm not sure if it totally solves the problem, but it's a start<|||||>@NielsRogge I'm looking about at this comment right now:

> Here's a notebook illustrating the issue, and fixing it:
> 
> https://colab.research.google.com/drive/10MbZiMKyEWUGk2Y1fvIj0Y0_lB42NO38?usp=sharing
> 
> The reason why you're getting the error is because in the part where each cell of the table is replaced by a Cell object:
> 
> https://github.com/huggingface/transformers/blob/97e688bc220514cd5ea072f06b186401c9cfbbd0/src/transformers/models/tapas/tokenization_tapas.py#L2742-L2745
> , the row indices are used.
> 
> This can be fixed by replacing `table` with `table.reset_index(drop=True)` in the first line (or resetting the index of the table before providing it to the tokenizer). Another solution is to replace the final line by `table.iloc[row_index, col_index] = Cell(text=table.iloc[row_index, col_index])`. Will make a small PR to add this.
> 
> Thank you for spotting the error!


I'm wondering if there's any performance improvement in iterating this way through the dataframe over something like:

```python
df.applymap(lambda cell: Cell(text=cell))
```<|||||>This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/master/CONTRIBUTING.md) are likely to be ignored.<|||||>@NielsRogge has this been resolved? 