leveldb: fix OpenTransaction godoc
diff --git a/leveldb/db_transaction.go b/leveldb/db_transaction.go
index 39c8a5a..5deb57e 100644
--- a/leveldb/db_transaction.go
+++ b/leveldb/db_transaction.go
@@ -263,7 +263,8 @@
// until in-flight transaction is committed or discarded.
// The returned transaction handle is safe for concurrent use.
//
-// Transaction is expensive and put restrains on the compaction.
+// Transaction is expensive and can overwhelm compaction, especially if
+// transaction size is small. Use with caution.
//
// The transaction must be closed once done, either by committing or discarding
// the transaction.
