Make team descriptions consistent

[HarrisonMc555]

Currently, each (some?) teams have descriptions. These appear at https://www.rust-lang.org/governance. However, there is little consistency in how they are formatted. Some start with capital letters and some don't; some have periods and some don't.

It would be great if each description was formatted the same way and with the same tense and "voice" (active, passive, etc.).

This is somewhat of a duplicate of rust-lang/www.rust-lang.org#560, but I figured it would be good to have an issue in this repository.