Remove sparse+ prefix for index.crates.io

Author: arlosi

src/cargo/sources/registry/mod.rs

@@ -188,7 +188,7 @@ use crate::util::{
 
 const PACKAGE_SOURCE_LOCK: &str = ".cargo-ok";
 pub const CRATES_IO_INDEX: &str = "https://github.com/rust-lang/crates.io-index";
-pub const CRATES_IO_HTTP_INDEX: &str = "sparse+https://index.crates.io/";
+pub const CRATES_IO_HTTP_INDEX: &str = "https://index.crates.io/";
 pub const CRATES_IO_REGISTRY: &str = "crates-io";
 pub const CRATES_IO_DOMAIN: &str = "crates.io";
 const CRATE_TEMPLATE: &str = "{crate}";