Fix ChestX-ray14 Example Notebooks

[EricSchrock]

In #392, I added the chestxray14_binary_classification.ipynb and chestxray14_multilabel_classification.ipynb examples. This PR cleans up three issues with these example notebooks.

1. PyHealth Install
2. GitHub Display
3. Duplicate Output

1. PyHealth Install

Previously, these notebooks installed PyHealth from a branch in my fork. Now that #392 is merged AND 2.0.0 is released, that can be cleaned up.

Before

!rm -rf PyHealth
!git clone https://github.com/EricSchrock/PyHealth.git
%cd PyHealth
!git checkout ChestX-ray14
!pip install -e .

After

%pip install pyhealth ipywidgets

Caution

Is it a surprise that ipywidgets must also be explicitly installed? I get an error in base_dataset.py if I just pip install pyhealth.

2. GitHub Display

I initially generated these notebooks in Google Colab. Apparently, this added a bunch of metadata, which wasn't compatible with the GitHub web UI. Trying to view the notebooks on GitHub would show the following. This PR should fix the issue.

3. Duplicate Output

The old versions of the example notebooks printed every output twice, which makes the example much longer and less clear. Apparently, I didn't have Google Colab properly configured to work with the Python logger. This PR fixes the duplicate output.

[jhnwu3]

lgtm!