Can't install tf2 on M1 Chip by default
# What does this PR do?

Trying to 
```
pip install 'transformers[tf-cpu]'
```

will give you a confusing error like below
```
Collecting sentencepiece==0.1.91
  Using cached sentencepiece-0.1.91.tar.gz (500 kB)
  Preparing metadata (setup.py) ... error
  error: subprocess-exited-with-error
  
  × python setup.py egg_info did not run successfully.
  │ exit code: 1
  ╰─> [5 lines of output]
      Package sentencepiece was not found in the pkg-config search path.
      Perhaps you should add the directory containing `sentencepiece.pc'
      to the PKG_CONFIG_PATH environment variable
      No package 'sentencepiece' found
      Failed to find sentencepiece pkgconfig
      [end of output]

```

The answer is to install `cmake` and `pkg-config` based on the reply here: 
https://github.com/google/sentencepiece/issues/378#issuecomment-969896519

## Before submitting
- [x] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
- [ ] Did you read the [contributor guideline](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md#start-contributing-pull-requests),
      Pull Request section?
- [ ] Was this discussed/approved via a Github issue or the [forum](https://discuss.huggingface.co/)? Please add a link
      to it if that's the case.
- [ ] Did you make sure to update the documentation with your changes? Here are the
      [documentation guidelines](https://github.com/huggingface/transformers/tree/main/docs), and
      [here are tips on formatting docstrings](https://github.com/huggingface/transformers/tree/main/docs#writing-source-documentation).
- [ ] Did you write any new necessary tests?


## Who can review?
@sgugger, @stevhliu and @MKhalusova
This actually got worse... if you open a new Laptop, you also have to do the following
```
brew install cmake
brew install pkg-config
brew install sentencepiece
pip install sentencepiece
```

and then I had to also install Rust next...
```
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
source "$HOME/.cargo/env"
```

After that, it finally works
```
pip install 'transformers[tf-cpu]'
```

Not sure how thorough we want to be in the docs of getting people fully up to speed vs. making certain assumptions. The `sentencepiece` part was fairly brutal to work through<|||||>_The documentation is not available anymore as the PR was closed or merged._