fix: events: fix event decoding

Events were already decoded on insertion. All we need to do is pad keys
to 32 bytes.

chain/events/filter/index.go

@@ -486,18 +486,14 @@ func (ei *EventIndex) RunMigration(from, to int) error {
 		if err := rows.Scan(&key, &before); err != nil {
 			return xerrors.Errorf("failed to scan from query: %w", err)
 		}
-		after, err := cbg.ReadByteArray(bytes.NewReader(before), 4<<20)
-		if err != nil {
-			return xerrors.Errorf("failed to decode cbor: %w; value: %s", err, hex.EncodeToString(before))
-		}
+		// If the key isn't 32 bytes, pad it.
 		if _, ok := topics[key]; ok && len(before) < 32 {
 			// if this is a topic, leftpad to 32 bytes
 			pvalue := make([]byte, 32)
-			copy(pvalue[32-len(after):], after)
-			after = pvalue
-		}
-		if _, err := update.Exec(after, before); err != nil {
-			return xerrors.Errorf("failed to scan from query: %w", err)
+			copy(pvalue[32-len(before):], before)
+			if _, err := update.Exec(pvalue, before); err != nil {
+				return xerrors.Errorf("failed to scan from query: %w", err)
+			}
 		}
 
 		if i++; i%500 == 0 {