state: fix block event indexing reserved key check (#6314)

copy 🍝  bug when porting similar logic from the tx indexing code.

state/indexer/block/kv/kv.go

@@ -469,9 +469,10 @@ func (idx *BlockerIndexer) indexEvents(batch dbm.Batch, events []abci.Event, typ
 
 			// index iff the event specified index:true and it's not a reserved event
 			compositeKey := fmt.Sprintf("%s.%s", event.Type, string(attr.Key))
-			if compositeKey == types.TxHashKey || compositeKey == types.TxHeightKey {
+			if compositeKey == types.BlockHeightKey {
 				return fmt.Errorf("event type and attribute key \"%s\" is reserved; please use a different key", compositeKey)
 			}
+
 			if attr.GetIndex() {
 				key, err := eventKey(compositeKey, typ, string(attr.Value), height)
 				if err != nil {