Correcting path to pplm examples
# 🐛 Bug

On https://github.com/huggingface/transformers/tree/master/examples/text-generation/pplm#setup

It says

```
git clone https://github.com/huggingface/transformers && cd transformers
pip install .
pip install nltk torchtext # additional requirements.
cd examples/pplm


```

and as you can guess from the url, the correct path is

```
git clone https://github.com/huggingface/transformers && cd transformers
pip install .
pip install nltk torchtext # additional requirements.
cd examples/text-generation/pplm
```


cd examples/**text-generation**/pplm

Thanks for the report – care to open a PR?<|||||>Done
https://github.com/huggingface/transformers/pull/4778

I hope it is done well.