Update rust-toolchain.toml
This matches the version actually used by Redox OS. It also supports the sparse index, which prevents having to clone the crates.io registry git repo when rust-analyzer tries to run cargo metadata on relibc.
This matches the version actually used by Redox OS. It also supports the sparse index, which prevents having to clone the crates.io registry git repo when rust-analyzer tries to run cargo metadata on relibc.