Remove italicised units in labels of SDEC plot in matplotlib

[jaladh-singhal]

To remove the italicised units, you could try something along the lines of:
plt.ylabel('Luminosity (erg $\mathrm{s^{-1}}$ $\mathrm{\AA^{-1}}$)')
This is an example where the labels won't be italicised, since they are in \mathrm{}

Originally posted by @jamesgillanders in #1442 (comment)