Update monitor update cleanup docs

Author: G8XSU

lightning/src/util/persist.rs

@@ -347,9 +347,10 @@ where
 ///
 /// # Pruning stale channel updates
 ///
-/// Stale updates are pruned when a full monitor is written. The old monitor is first read, and if
-/// that succeeds, updates in the range between the old and new monitors are deleted. The `lazy`
-/// flag is used on the [`KVStore::remove`] method, so there are no guarantees that the deletions
+/// Stale updates are pruned when consolidation threshold is reached according to `maximum_pending_updates`.
+/// Monitor updates in the range between the latest `update_id` and `update_id - maximum_pending_updates`
+/// are deleted.
+/// The `lazy` flag is used on the [`KVStore::remove`] method, so there are no guarantees that the deletions
 /// will complete. However, stale updates are not a problem for data integrity, since updates are
 /// only read that are higher than the stored [`ChannelMonitor`]'s `update_id`.
 ///