Transition to Edition 2021

We need to bump the MSRV to 1.60 anyway in later commits, so why not
switch to the new edition.

Author: LukasKalbertodt

Cargo.toml

@@ -2,7 +2,7 @@
 name = "atomig"
 version = "0.3.3"
 authors = ["Lukas Kalbertodt <lukas.kalbertodt@gmail.com>"]
-edition = "2018"
+edition = "2021"
 
 description = """
 Generic and convenient `std` atomics via `Atomic<T>`. Can be used with many

atomig-macro/Cargo.toml

@@ -2,7 +2,7 @@
 name = "atomig-macro"
 version = "0.2.0"
 authors = ["Lukas Kalbertodt <lukas.kalbertodt@gmail.com>"]
-edition = "2018"
+edition = "2021"
 
 description = """
 Defines procedural macros for the crate `atomig`. Please see the main crate.

src/impls.rs

@@ -344,7 +344,6 @@ impl Atom for char {
         self.into()
     }
     fn unpack(src: Self::Repr) -> Self {
-        use core::convert::TryFrom;
         Self::try_from(src).expect("invalid value in <char as Atom>::unpack")
     }
 }