Incorrect docs for "only test these crates"?

[RalfJung]

The docs seem to say that the syntax for building only a subset of crates is something like list:$URL. However, that syntax does not seem to work. The actual syntax is crates=$URL.

[Skgland]

I think this can be closed as the docs have been updated.

[RalfJung]

Specifically, this got fixed by #784. Thanks!