Plotter Warnings

[ax3l]

With Python 3.12 and the latest openPMD-viewer 1.10.0 release, I see the following warnings:

openpmd_viewer/openpmd_timeseries/plotter.py:311: SyntaxWarning: invalid escape sequence '\;'
  plt.xlabel('$%s \;(m)$' % info.axes[0], fontsize=self.fontsize)
openpmd_viewer/openpmd_timeseries/plotter.py:389: SyntaxWarning: invalid escape sequence '\;'
  plt.xlabel('$%s \;(m)$' % info.axes[1], fontsize=self.fontsize)
openpmd_viewer/openpmd_timeseries/plotter.py:390: SyntaxWarning: invalid escape sequence '\;'
  plt.ylabel('$%s \;(m)$' % info.axes[0], fontsize=self.fontsize)