Remove the last bits of unknown_os in the code base (#9718)

* Remove the last bits of unknown_os in the code base

* Fmt

substrate/client/offchain/src/api.rs

@@ -32,14 +32,8 @@ use sp_core::{
 };
 pub use sp_offchain::STORAGE_PREFIX;
 
-#[cfg(not(target_os = "unknown"))]
 mod http;
 
-#[cfg(target_os = "unknown")]
-use http_dummy as http;
-#[cfg(target_os = "unknown")]
-mod http_dummy;
-
 mod timestamp;
 
 fn unavailable_yet<R: Default>(name: &str) -> R {