Document the impact of the redjubjub channel bound

zebra-consensus/src/primitives/redjubjub.rs

@@ -62,8 +62,9 @@ pub struct Verifier {
 impl Default for Verifier {
     fn default() -> Self {
         let batch = batch::Verifier::default();
-        // This bound should be big enough to avoid RecvErrors
-        // when tasks wait on results for a long time.
+        // This bound limits the number of concurrent batches. It should be
+        // big enough to avoid RecvErrors when tasks wait on results for a long
+        // time.
         let (tx, _) = channel(512);
         Self { tx, batch }
     }