Remove Rust async feature

Author: wysaid

bindings/rust/Cargo.lock

@@ -13,9 +13,7 @@ readme = "README.md"
 keywords = ["camera", "capture", "v4l2", "directshow", "avfoundation"]
 categories = ["multimedia::video", "api-bindings"]
 
-[package.metadata.docs.rs]
-# Build docs with async API enabled so users can see `ccap::r#async::*` on docs.rs.
-features = ["async"]
+
 
 [lib]
 # Keep the Rust crate name as `ccap` so users can write:
@@ -25,15 +23,13 @@ name = "ccap"
 
 [dependencies]
 thiserror = "1.0"
-tokio = { version = "1.0", features = ["full"], optional = true }
 
 [build-dependencies]
 bindgen = "0.68"
 cc = "1.0"
 
 [features]
 default = ["build-source"]
-async = ["tokio"]
 static-link = [] # Link against pre-built static library (for development)
 build-source = [] # Build from source using cc crate (for distribution)