Switch to shields.io PyPI badge with more sigfigs
<td>PyPI</td>
<td>
<a href="https://docs.bokeh.org/en/latest/docs/installation.html">
- <img src="https://pepy.tech/badge/bokeh/month"
+ <img src="https://img.shields.io/pypi/dm/bokeh"
alt="PyPI downloads per month" />
</a>
</td>
