core/state: ignore the root returned in Commit function for simplicity (#34723)

StateDB.Commit first commits all storage changes into the storage trie,
then updates the account metadata with the new storage root into the 
account trie.

Within StateDB.Commit, the new storage trie root has already been
computed and applied as the storage root. This PR explicitly skips the 
redundant storage trie root assignment for readability.

core/state/state_object.go

@@ -482,8 +482,9 @@ func (s *stateObject) commit() (*accountUpdate, *trienode.NodeSet, error) {
 		s.origin = s.data.Copy()
 		return op, nil, nil
 	}
-	root, nodes := s.trie.Commit(false)
-	s.data.Root = root
+	// The storage trie root is omitted, as it has already been updated in the
+	// previous updateRoot step.
+	_, nodes := s.trie.Commit(false)
 	s.origin = s.data.Copy()
 	return op, nodes, nil
 }

core/state/statedb.go

@@ -1162,7 +1162,7 @@ func (s *StateDB) commit(deleteEmptyObjects bool, noStorageWiping bool, blockNum
 		return nil, fmt.Errorf("commit aborted due to earlier error: %v", s.dbErr)
 	}
 	// Finalize any pending changes and merge everything into the tries
-	s.IntermediateRoot(deleteEmptyObjects)
+	root := s.IntermediateRoot(deleteEmptyObjects)
 
 	// Short circuit if any error occurs within the IntermediateRoot.
 	if s.dbErr != nil {
@@ -1224,7 +1224,6 @@ func (s *StateDB) commit(deleteEmptyObjects bool, noStorageWiping bool, blockNum
 	// writes to run in parallel with the computations.
 	var (
 		start   = time.Now()
-		root    common.Hash
 		workers errgroup.Group
 	)
 	// Schedule the account trie first since that will be the biggest, so give
@@ -1238,9 +1237,7 @@ func (s *StateDB) commit(deleteEmptyObjects bool, noStorageWiping bool, blockNum
 	// code didn't anticipate for.
 	workers.Go(func() error {
 		// Write the account trie changes, measuring the amount of wasted time
-		newroot, set := s.trie.Commit(true)
-		root = newroot
-
+		_, set := s.trie.Commit(true)
 		if err := merge(set); err != nil {
 			return err
 		}