Style fix

Author: Mairbek Khadikov

sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/spanner/SpannerIO.java

@@ -81,10 +81,12 @@
  * batching.
  *
  * <p>The transform does not provide same transactional guarantees as Cloud Spanner. In particular,
+ * <ul>
  * <li>Mutations are not submitted atomically;
  * <li>A mutation is applied at least once;
  * <li>If the pipeline was unexpectedly stopped, mutations that were already applied will not get
  *     rolled back.
+ * </ul>
  */
 @Experimental(Experimental.Kind.SOURCE_SINK)
 public class SpannerIO {