Increase maximum chunk size to adjust for small networks. (#4220)

* Increase maximum chunk size to adjust for small networks.

* Issue warning on invalid merkle proofs.

* warn -> debug on invalid merkle proof.

polkadot/node/network/protocol/src/request_response/mod.rs

@@ -133,7 +133,7 @@ impl Protocol {
 			Protocol::ChunkFetching => RequestResponseConfig {
 				name: p_name,
 				max_request_size: 1_000,
-				max_response_size: POV_RESPONSE_SIZE as u64 / 10,
+				max_response_size: POV_RESPONSE_SIZE as u64 * 3,
 				// We are connected to all validators:
 				request_timeout: CHUNK_REQUEST_TIMEOUT,
 				inbound_queue: Some(tx),