Update MSRV to 1.68

Author: james7132

Cargo.toml

@@ -6,7 +6,7 @@ name = "async-executor"
 version = "1.13.2"
 authors = ["Stjepan Glavina <[email protected]>", "John Nunley <[email protected]>"]
 edition = "2021"
-rust-version = "1.63"
+rust-version = "1.68"
 description = "Async executor"
 license = "Apache-2.0 OR MIT"
 repository = "https://github.com/smol-rs/async-executor"
@@ -36,7 +36,7 @@ futures-lite = { version = "2.0.0", default-features = false, features = ["std"]
 async-channel = "2.0.0"
 async-io = "2.1.0"
 async-lock = "3.0.0"
-criterion = { version = "0.5", default-features = false, features = ["cargo_bench_support"] }
+criterion = { version = "0.6", default-features = false, features = ["cargo_bench_support"] }
 easy-parallel = "3.1.0"
 fastrand = "2.0.0"
 futures-lite = "2.0.0"