Migrate to snippet to avoid HTML formatting issues (#5555)

Author: dagnir

services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/mapper/annotations/DynamoDbPreserveEmptyObject.java

@@ -31,13 +31,13 @@
  * <p>
  * Example using {@link DynamoDbPreserveEmptyObject}:
  * <pre>
- * <code>
- * &#64;DynamoDbBean
+ * {@snippet :
+ * @DynamoDbBean
  * public class NestedBean {
  *     private AbstractBean innerBean1;
  *     private AbstractBean innerBean2;
  *
- *     &#64;DynamoDbPreserveEmptyObject
+ *     @DynamoDbPreserveEmptyObject
  *     public AbstractBean getInnerBean1() {
  *         return innerBean1;
  *     }
@@ -69,7 +69,7 @@
  *
  * // innerBean2 w/o @DynamoDbPreserveEmptyObject is mapped to null.
  * assertThat(nestedBean.getInnerBean2(), isNull());
- * </code>
+ * }
  * </pre>
  */
 @SdkPublicApi