Simplify some Option / Result / ? operator patterns (#2920)

* Simplify some Option / Result / ? operator patterns

When they identically match a combinator on those types.

Tool-aided by [comby-rust](https://github.com/huitseeker/comby-rust).

* adjust review comments

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>

polkadot/node/network/statement-distribution/src/lib.rs

@@ -1308,12 +1308,7 @@ async fn handle_incoming_message<'a>(
 		ctx,
 		req_sender,
 		metrics,
-	).await;
-
-	let statement = match statement {
-		None => return None,
-		Some(statement) => statement,
-	};
+	).await?;
 
 	match active_head.check_useful_or_unknown(statement.clone()) {
 		Ok(()) => {},