Fix prelude imports

Remove imports that are reported as unused by the nightly compiler,
override the lint for the vec macro import that is actually used.

config/src/prelude.rs

@@ -2,7 +2,6 @@
 // https://doc.rust-lang.org/src/alloc/prelude/v1.rs.html
 pub use alloc::{
     borrow::ToOwned,
-    boxed::Box,
     format,
     string::{String, ToString},
     vec,

light-client-verifier/src/prelude.rs

@@ -1,13 +1,10 @@
 // Re-export according to alloc::prelude::v1 because it is not yet stabilized
 // https://doc.rust-lang.org/src/alloc/prelude/v1.rs.html
+#[allow(unused_imports)]
 pub use alloc::{
-    borrow::ToOwned,
     boxed::Box,
-    format,
     string::{String, ToString},
     vec,
     vec::Vec,
 };
-// will be included in 2021 edition.
-pub use core::convert::{TryFrom, TryInto};
 pub use core::prelude::v1::*;

proto/src/prelude.rs

@@ -2,10 +2,8 @@
 // https://doc.rust-lang.org/src/alloc/prelude/v1.rs.html
 pub use alloc::{
     borrow::ToOwned,
-    boxed::Box,
     format,
     string::{String, ToString},
-    vec,
     vec::Vec,
 };
 pub use core::prelude::v1::*;