Clarify intended nestedTransactionAllowed default in JpaTransactionManager

Closes gh-35212

spring-orm/src/main/java/org/springframework/orm/hibernate5/HibernateTransactionManager.java

@@ -88,12 +88,12 @@ import org.springframework.util.Assert;
  * such a scenario (see container setup).
  *
  * <p>This transaction manager supports nested transactions via JDBC Savepoints.
- * The {@link #setNestedTransactionAllowed} "nestedTransactionAllowed"} flag defaults
+ * The {@link #setNestedTransactionAllowed "nestedTransactionAllowed"} flag defaults
  * to "false", though, as nested transactions will just apply to the JDBC Connection,
  * not to the Hibernate Session and its cached entity objects and related context.
  * You can manually set the flag to "true" if you want to use nested transactions
  * for JDBC access code which participates in Hibernate transactions (provided that
- * your JDBC driver supports Savepoints). <i>Note that Hibernate itself does not
+ * your JDBC driver supports savepoints). <i>Note that Hibernate itself does not
  * support nested transactions! Hence, do not expect Hibernate access code to
  * semantically participate in a nested transaction.</i>
  *

spring-orm/src/main/java/org/springframework/orm/jpa/JpaTransactionManager.java

@@ -93,13 +93,14 @@ import org.springframework.util.CollectionUtils;
  *
  * <p>This transaction manager supports nested transactions via JDBC Savepoints.
  * The {@link #setNestedTransactionAllowed "nestedTransactionAllowed"} flag defaults
- * to {@code false} though, since nested transactions will just apply to the JDBC
- * Connection, not to the JPA EntityManager and its cached entity objects and related
- * context. You can manually set the flag to {@code true} if you want to use nested
- * transactions for JDBC access code which participates in JPA transactions (provided
- * that your JDBC driver supports Savepoints). <i>Note that JPA itself does not support
- * nested transactions! Hence, do not expect JPA access code to semantically
- * participate in a nested transaction.</i>
+ * to "true" but should rather be "false", as nested transactions will just apply to
+ * the JDBC Connection, not to the JPA EntityManager and its cached entity objects
+ * and related context. As of Spring Framework 7.0, the default will be "false" in
+ * alignment with other transaction managers, requiring an explicit switch to "true"
+ * if you want to use nested transactions for JDBC access code which participates
+ * in JPA transactions (provided that your JDBC driver supports savepoints).
+ * <i>Note that JPA itself does not support nested transactions! Hence, do not
+ * expect JPA access code to semantically participate in a nested transaction.</i>
  *
  * @author Juergen Hoeller
  * @since 2.0