Add Javadoc since for BeanDefinitionValueResolver.resolveInnerBean()

See gh-28217

spring-beans/src/main/java/org/springframework/beans/factory/support/BeanDefinitionValueResolver.java

@@ -252,6 +252,7 @@ else if (value instanceof NullBean) {
 	 * @param resolver the function to invoke to resolve
 	 * @param <T> the type of the resolution
 	 * @return a resolved inner bean, as a result of applying the {@code resolver}
+	 * @since 6.0
 	 */
 	public <T> T resolveInnerBean(@Nullable String innerBeanName, BeanDefinition innerBd,
 			BiFunction<String, RootBeanDefinition, T> resolver) {