Remove unused font variants

[avkvirtru]

For future, more disciplined designs, Virtru probably doesn't need all the variants of Open Sans and Raleway. But today, we can't delete the less common variants without knowing what's out there in production.

Let's document what fonts are used in each Virtru product and remove anything that remains.

[avkvirtru]

Fonts in Dashboard: https://github.com/virtru/dashboard/blob/master/src/stylesheets/_text.scss