Need to update setup.py description

In our setup.py file, we say we are using markdown:

-    description="Convert trained traditional machine learning models into tensor computations",
-    long_description=long_description,
-    long_description_content_type="text/markdown",

Pypi was not loving this.

Uploading hummingbird_ml-0.4.11-py2.py3-none-any.whl
100% ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 174.8/174.8 kB • 00:00 • 1.1 MB/s
INFO     Response from https://upload.pypi.org/legacy/:
         400 The description failed to render in the default format of reStructuredText. See https://pypi.org/help/#description-content-type for more information.
    <html>
          <head>
           <title>400 The description failed to render in the default format of reStructuredText. See https://pypi.org/help/#description-content-type for more information.</title>
          </head>
          <body>
           <h1>400 The description failed to render in the default format of reStructuredText. See https://pypi.org/help/#description-content-type for more information.</h1>
           The server could not comply with the request since it is either malformed or otherwise incorrect.<br/><br/>
         The description failed to render in the default format of reStructuredText. See https://pypi.org/help/#description-content-type for more information.

          </body>
         </html>
ERROR    HTTPError: 400 Bad Request from https://upload.pypi.org/legacy/
         The description failed to render in the default format of reStructuredText. See https://pypi.org/help/#description-content-type for more information.

For now just deleted these 3 lines, but we should change the format away from markdown. See docs

microsoft / hummingbird

Need to update setup.py description #766