Fira Sans Thin has wrong weight

On the [Fira Sans specimen page](https://fonts.google.com/specimen/Fira+Sans), Thin is listed as weight 100.

If you download from that page, and run fontconfig on it, i.e., `fc-scan FiraSansThin.ttf`, you get `weight: 45.5(f)(s)`. If you open it in FontForge, and go to Element->Font Info, the Weight is _Light_.

If instead, you grab the files from the [original creator's release](https://github.com/mozilla/Fira/releases/tag/4.202), and run fontconfig on it, you get `weight: 0(f)(s)`, and if you open it in FontForge, the Weight is Thin, as expected.

The same is true of Thin Italic.