io: Move use statement

Use the newly settled upon policy governing layout for imports.

io/src/lib.rs

@@ -23,11 +23,11 @@ extern crate alloc;
 mod error;
 mod macros;
 
+use core::convert::TryInto;
+
 #[rustfmt::skip]                // Keep public re-exports separate.
 pub use self::error::{Error, ErrorKind};
 
-use core::convert::TryInto;
-
 pub type Result<T> = core::result::Result<T, Error>;
 
 /// A generic trait describing an input stream. See [`std::io::Read`] for more info.