Simplify some Option / Result / ? operator patterns (#8653)

* Simplify some Option / Result / ? operator patterns

When those match a combinator exactly.

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

* adjust after review

* adjust post-review

substrate/client/transaction-pool/graph/src/pool.rs

@@ -322,10 +322,7 @@ impl<B: ChainApi> Pool<B> {
 	) -> Result<(), B::Error> {
 		log::debug!(target: "txpool", "Pruning at {:?}", at);
 		// Prune all transactions that provide given tags
-		let prune_status = match self.validated_pool.prune_tags(tags) {
-			Ok(prune_status) => prune_status,
-			Err(e) => return Err(e),
-		};
+		let prune_status = self.validated_pool.prune_tags(tags)?;
 
 		// Make sure that we don't revalidate extrinsics that were part of the recently
 		// imported block. This is especially important for UTXO-like chains cause the

substrate/client/transaction-pool/graph/src/ready.rs

@@ -527,12 +527,9 @@ impl<Hash: hash::Hash + Member, Ex> Iterator for BestIterator<Hash, Ex> {
 					satisfied += 1;
 					Some((satisfied, tx_ref))
 				// then get from the pool
-				} else if let Some(next) = self.all.read().get(hash) {
-					Some((next.requires_offset + 1, next.transaction.clone()))
 				} else {
-					None
+					self.all.read().get(hash).map(|next| (next.requires_offset + 1, next.transaction.clone()))
 				};
-
 				if let Some((satisfied, tx_ref)) = res {
 					self.best_or_awaiting(satisfied, tx_ref)
 				}