backing-availability-audit: Move ErasureChunk Proof to BoundedVec (#3626)

* backing-availability-audit: Move ErasureChunk Proof to BoundedVec

* WIP

* Touch up

* Fix spelling mistake

* Address Feedback

polkadot/node/network/protocol/src/request_response/v1.rs

@@ -19,7 +19,7 @@
 use parity_scale_codec::{Decode, Encode};
 
 use polkadot_node_primitives::{
-	AvailableData, DisputeMessage, ErasureChunk, PoV, UncheckedDisputeMessage,
+	AvailableData, DisputeMessage, ErasureChunk, PoV, Proof, UncheckedDisputeMessage,
 };
 use polkadot_primitives::v1::{
 	CandidateHash, CandidateReceipt, CommittedCandidateReceipt, Hash, Id as ParaId, ValidatorIndex,
@@ -67,7 +67,7 @@ pub struct ChunkResponse {
 	/// The erasure-encoded chunk of data belonging to the candidate block.
 	pub chunk: Vec<u8>,
 	/// Proof for this chunk's branch in the Merkle tree.
-	pub proof: Vec<Vec<u8>>,
+	pub proof: Proof,
 }
 
 impl From<ErasureChunk> for ChunkResponse {