Move futures-lite to dev-dependencies

This dependency is only used by `examples/`. Moving it to
`dev-dependencies` prevents it from being propagated to users of the
library.

Cargo.toml

@@ -11,13 +11,13 @@ repository = "https://github.com/kevinmehall/nusb"
 
 [dependencies]
 atomic-waker = "1.1.2"
-futures-lite = "1.13.0"
 log = "0.4.20"
 once_cell = "1.18.0"
 slab = "0.4.9"
 
 [dev-dependencies]
 env_logger = "0.10.0"
+futures-lite = "1.13.0"
 
 [target.'cfg(target_os="linux")'.dependencies]
 rustix = { version = "0.38.17", features = ["fs", "event"] }