Update Rust crate async-trait to 0.1.68 (#8)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

async-vfs/Cargo.toml

@@ -11,6 +11,6 @@ readme = "../README.md"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-async-trait = "0.1.42"
+async-trait = "0.1.68"
 futures-lite = "1.12.0"
 thiserror = "1.0.40"