Aggregate subsets (#3493)

## Issue Addressed

Resolves #3238 

## Proposed Changes

Please list or describe the changes introduced by this PR.

## Additional Info

Please provide any additional information. For example, future considerations
or information useful for reviewers.

beacon_node/http_api/src/lib.rs

@@ -2843,7 +2843,7 @@ pub fn serve<T: BeaconChainTypes>(
                             // It's reasonably likely that two different validators produce
                             // identical aggregates, especially if they're using the same beacon
                             // node.
-                            Err(AttnError::AttestationAlreadyKnown(_)) => continue,
+                            Err(AttnError::AttestationSupersetKnown(_)) => continue,
                             // If we've already seen this aggregator produce an aggregate, just
                             // skip this one.
                             //

beacon_node/http_api/src/sync_committees.rs

@@ -304,7 +304,7 @@ pub fn process_signed_contribution_and_proofs<T: BeaconChainTypes>(
             }
             // If we already know the contribution, don't broadcast it or attempt to
             // further verify it. Return success.
-            Err(SyncVerificationError::SyncContributionAlreadyKnown(_)) => continue,
+            Err(SyncVerificationError::SyncContributionSupersetKnown(_)) => continue,
             // If we've already seen this aggregator produce an aggregate, just
             // skip this one.
             //