docs.rs pages are left-aligned

[jyn514]

This is a regression introduced by #1079 - only the /crate pages should be left-aligned, not /about and index. cc @jsha , do you think you have time to follow-up and fix this? I think a simple fix would be to only apply left-aligns to /crate pages, not sure if we have custom CSS for them yet but it shouldn't be too hard to add.

[jsha]

Oops, sorry about that! I'll send a fix.