Cargo.lock: update `cargo_metadata` to 0.6.1 release
Cargo.lock: update `cargo_metadata` to 0.6.1 release

The update is especially important as it adds support for the
`edition` field handling, when parsing `cargo` metadata.

Refs: #3104.

Signed-off-by: Otavio Salvador <1d31b11c1b92bf5d043d36edfe7174db39a6b891@ossystems.com.br>

graydon/rust,SingingTree/rustfmt,aidancully/rust,rust-lang/rustfmt,graydon/rust,aidancully/rust,SingingTree/rustfmt,aidancully/rust,graydon/rust,rust-lang/rustfmt,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust