fix(tonic): Remove Sync requirement for streams (#804)

examples/src/multiplex/server.rs

@@ -20,7 +20,7 @@ use echo::{
     EchoRequest, EchoResponse,
 };
 
-type ResponseStream = Pin<Box<dyn Stream<Item = Result<EchoResponse, Status>> + Send + Sync>>;
+type ResponseStream = Pin<Box<dyn Stream<Item = Result<EchoResponse, Status>> + Send>>;
 
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {