Cargo warning during `x.py build`: "the cargo feature `edition` is now stable"

[RalfJung]

Plenty of lines like the following are printed during a build:

warning: the cargo feature `edition` is now stable and is no longer necessary to be listed in the manifest

This is likely caused by these:

src/tools/rls/Cargo.toml
1:cargo-features = ["edition"]

src/tools/clippy/Cargo.toml
1:cargo-features = ["edition"]

src/tools/clippy/rustc_tools_util/Cargo.toml
1:cargo-features = ["edition"]

src/tools/clippy/clippy_lints/Cargo.toml
1:cargo-features = ["edition"]

src/tools/clippy/clippy_dev/Cargo.toml
1:cargo-features = ["edition"]

[matthiaskrgr]

The clippy ones are already fixed upstream: rust-lang/rust-clippy#3242

[cuviper]

ISTR that 1.30-beta was only preview-stabilizing edition stuff, but that they'll be unstable in the 1.30 release. So when the current master branch forks off as 1.31-beta, it will still need to bootstrap with that 1.30 stable.

But if cargo is going to keep edition stable in 1.30, then we can go ahead and nuke those.

[RalfJung]

The clippy fix has landed in rustc. RLS also has a fix at rust-lang/rls#1074. What would it take to get that into rustc?

[matthiaskrgr]

Needs submodule update, I can do that this afternoon