Remove app that uses Boston housing prices dataset

doc/python/ml-pca.md

@@ -136,18 +136,6 @@ fig.update_traces(diagonal_visible=False)
 fig.show()
 ```
 
-## PCA analysis in Dash
-
-[Dash](https://plotly.com/dash/) is the best way to build analytical apps in Python using Plotly figures. To run the app below, run `pip install dash`, click "Download" to get the code and run `python app.py`.
-
-Get started  with [the official Dash docs](https://dash.plotly.com/installation) and **learn how to effortlessly [style](https://plotly.com/dash/design-kit/) & [deploy](https://plotly.com/dash/app-manager/) apps like this with <a class="plotly-red" href="https://plotly.com/dash/">Dash Enterprise</a>.**
-
-
-```python hide_code=true
-from IPython.display import IFrame
-snippet_url = 'https://python-docs-dash-snippets.herokuapp.com/python-docs-dash-snippets/'
-IFrame(snippet_url + 'pca-visualization', width='100%', height=1200)
-```
 
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