mixing latex and jinja templates causes jinja to fail, crashing the gunicorn server process

[bhpayne]

This is a rediscovery of the same issue described on leanprover-community/leanprover-community.github.io#168

The file logs/gunicorn_error.log contained the following failure trace:

  File "/home/appuser/app/templates/central_expressions.html", line 302, in template
    <td>\( \frac{\Delta p}{L} = f_\mathrm{D} \cdot \frac{\rho }{2} \cdot \frac{{\langle v \rangle}^2}{D} \)</td> <!-- expression -->
jinja2.exceptions.TemplateSyntaxError: unexpected char '\\' at 15981

[bhpayne]

Fix was to remove {{ from the latex. Now the line is

<td>\( \frac{\Delta p}{L} = f_{\mathrm{D}} \cdot \frac{\rho }{2} \cdot \frac{\langle v \rangle^2}{D} \)</td> <!-- expression -->