fix incorrect statement in the javadoc

apparently I don't know how Hibernate works

Author: gavinking

hibernate-core/src/main/java/org/hibernate/Session.java

@@ -46,11 +46,8 @@
  * <p>
  * Each persistent instance has a <em>persistent identity</em> determined by its type
  * and identifier value. There may be at most one persistent instance with a given
- * persistent identity associated with a given session. Normally, a persistent identity
- * is assigned when an {@linkplain #persist(Object) instance is made persistent}, but
- * when the entity identifier is {@linkplain org.hibernate.generator.OnExecutionGenerator
- * generated by the database}, assignment of the persistent identity is delayed until
- * the state of the entity is actually inserted in the database.
+ * persistent identity associated with a given session. A persistent identity is
+ * assigned when an {@linkplain #persist(Object) instance is made persistent}.
  * <p>
  * An instance of an entity class may be associated with at most one open session.
  * Distinct sessions represent state with the same persistent identity using distinct