title: Plotly fails to show text in Latex labels in Python
body: <p>I am using plotly to do some plots. I need to use math symbols in the labels of the axes. Plotly shows the latex parts but not the text parts:</p>
  <pre><code>import plotly.graph_objects as go
  import numpy as np
  
  x = np.array([1,2,3,4,5,6,7,8,9])
  
  fig = go.Figure()
  fig.add_trace(
      go.Scatter(
          x = x,
          y = x**2,
      )
  )
  fig.update_layout(
      title = 'My figure',
      xaxis_title = r'$\Delta t$ (s)',
      yaxis_title = r'This text is not displayed/$\sqrt{2}$ (ps)',
  )
  fig.show()
  </code></pre>
  <p>produces<a href="https://i.stack.imgur.com/hzGez.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/hzGez.png" alt="enter image description here" /></a></p>
  <p>Note that the text parts in the labels are not being displayed. I am using Python 3.8.5 with Plotly 4.9.0 and viewing the plots with Firefox 81.0.2 in Ubuntu 20.04.</p>