Update to superstruct v0.4.1 (#2886)

## Proposed Changes

Update `superstruct` to bring in @realbigsean's fixes necessary for MEV-compatible private beacon block types (a la #2795).

The refactoring is due to another change in superstruct that allows partial getters to be auto-generated.

consensus/types/src/beacon_block.rs

@@ -237,13 +237,8 @@ impl<'a, T: EthSpec> BeaconBlockRef<'a, T> {
 
     /// Extracts a reference to an execution payload from a block, returning an error if the block
     /// is pre-merge.
-    pub fn execution_payload(&self) -> Result<&ExecutionPayload<T>, InconsistentFork> {
-        self.body()
-            .execution_payload()
-            .ok_or_else(|| InconsistentFork {
-                fork_at_slot: ForkName::Merge,
-                object_fork: self.body().fork_name(),
-            })
+    pub fn execution_payload(&self) -> Result<&ExecutionPayload<T>, Error> {
+        self.body().execution_payload()
     }
 }
 

consensus/types/src/beacon_block_body.rs

@@ -50,24 +50,6 @@ pub struct BeaconBlockBody<T: EthSpec> {
 }
 
 impl<'a, T: EthSpec> BeaconBlockBodyRef<'a, T> {
-    /// Access the sync aggregate from the block's body, if one exists.
-    pub fn sync_aggregate(self) -> Option<&'a SyncAggregate<T>> {
-        match self {
-            BeaconBlockBodyRef::Base(_) => None,
-            BeaconBlockBodyRef::Altair(inner) => Some(&inner.sync_aggregate),
-            BeaconBlockBodyRef::Merge(inner) => Some(&inner.sync_aggregate),
-        }
-    }
-
-    /// Access the execution payload from the block's body, if one exists.
-    pub fn execution_payload(self) -> Option<&'a ExecutionPayload<T>> {
-        match self {
-            BeaconBlockBodyRef::Base(_) => None,
-            BeaconBlockBodyRef::Altair(_) => None,
-            BeaconBlockBodyRef::Merge(inner) => Some(&inner.execution_payload),
-        }
-    }
-
     /// Get the fork_name of this object
     pub fn fork_name(self) -> ForkName {
         match self {