Relax MSRV to 1.60

smol-rs/futures-lite#90

Author: taiki-e

Cargo.toml

@@ -6,7 +6,7 @@ name = "async-executor"
 version = "1.8.0"
 authors = ["Stjepan Glavina <stjepang@gmail.com>"]
 edition = "2021"
-rust-version = "1.61"
+rust-version = "1.60"
 description = "Async executor"
 license = "Apache-2.0 OR MIT"
 repository = "https://github.com/smol-rs/async-executor"