Apply suggestions from code review

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>

roadmap/implementers-guide/src/runtime/inclusion.md

@@ -70,7 +70,7 @@ All failed checks should lead to an unrecoverable error making the block invalid
   1. call `Router::check_upward_messages(para, commitments.upward_messages)` to check that the upward messages are valid.
   1. call `Router::check_processed_downward_messages(para, commitments.processed_downward_messages)` to check that the DMQ is properly drained.
   1. call `Router::check_hrmp_watermark(para, commitments.hrmp_watermark)` for each candidate to check rules of processing the HRMP watermark.
-  1. using `Router::check_outbound_hrmp(sender, commitments.horizontal_messages)` ensure that the each candidate send a valid set of horizontal messages
+  1. using `Router::check_outbound_hrmp(sender, commitments.horizontal_messages)` ensure that the each candidate sent a valid set of horizontal messages
   1. create an entry in the `PendingAvailability` map for each backed candidate with a blank `availability_votes` bitfield.
   1. create a corresponding entry in the `PendingAvailabilityCommitments` with the commitments.
   1. Return a `Vec<CoreIndex>` of all scheduled cores of the list of passed assignments that a candidate was successfully backed for, sorted ascending by CoreIndex.

roadmap/implementers-guide/src/runtime/router.md

@@ -92,8 +92,6 @@ struct HrmpChannel {
     sender_deposit: Balance,
     /// The amount that the recipient supplied as a deposit when accepting opening this channel.
     recipient_deposit: Balance,
-    /// The maximum message size that could be put into the channel.
-    limit_message_size: u32,
     /// The maximum number of messages that can be pending in the channel at once.
     max_capacity: u32,
     /// The maximum total size of the messages that can be pending in the channel at once.
@@ -173,7 +171,7 @@ HrmpChannelContents: map HrmpChannelId => Vec<InboundHrmpMessage>;
 /// Maintains a mapping that can be used to answer the question:
 /// What paras sent a message at the given block number for a given reciever.
 /// Invariants:
-/// - The para ids vector is never empty.
+/// - The inner `Vec<ParaId>` is never empty.
 /// - The para ids vector doesn't contain duplicates.
 /// - The outer vector is sorted ascending by block number and there are no duplicates.
 HrmpChannelDigests: map ParaId => Vec<(BlockNumber, Vec<ParaId>)>;

runtime/parachains/src/router/hrmp.rs

@@ -973,7 +973,7 @@ mod tests {
 		//   (a, x)         (a, x)
 		//   (a, y)         (a, y)
 		//   (b, x)         (b, x)
-		//   (b, y)         (b, y)
+		//   (b, z)         (b, z)
 		//
 		// and then that we compare that to the channel list in the `HrmpChannels`.
 		let channel_set_derived_from_ingress = <Router as Store>::HrmpIngressChannelsIndex::iter()