devel/cargo: update to 0.10.0 to unbreak after r416219

Newer bootstrap snapshots are required, so update src/snapshots.txt
based on rustup verbose output[1]. I couldn't find one for DragonFly.

$ fetch -o /tmp/rustup.sh https://sh.rustup.rs
$ sh /tmp/rustup.sh -v
[...]
https://static.rust-lang.org/dist/channel-rust-stable.toml
[...]
https://static.rust-lang.org/cargo-dist/2016-04-10/cargo-nightly-x86_64-unknown-freebsd.tar.gz

PR: 210017
Reported by: pkg-fallout, Lacey Powers
Reported by: dumbbell (maintainer) [1]