Change dependency format in Cargo.toml

[clangenb]

We discussed the formatting of dependencies in Cargo.toml in In #328.

We came to the conclusion that the overall readability is improved if we use the one-line format compared to the multi-line.

E.g.
Good:

frame-metadata = { version = "13.0.0", default-features = false, git = "https://github.com/paritytech/substrate.git", branch = "master"}

bad:

[dependencies.sp-runtime]
git = "https://github.com/paritytech/substrate.git"
branch = "master"
version = "3.0.0"
default-features = false