grammar fix in jdoc

Author: gavinking

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

@@ -54,8 +54,8 @@
  * Certain rules applying to stateful sessions are relaxed in a stateless
  * session:
  * <ul>
- * <li>it is not necessary to discard a session and its entities after an
- *     exception is thrown by a stateless sessions, and
+ * <li>it's not necessary to discard a stateless session and its entities
+ *     after an exception is thrown by the stateless session, and
  * <li>when an exception is thrown by a stateless session, the current
  *     transaction is not automatically marked for rollback.
  * </ul>