HBASE-18582 Correct the docs for Mutation#setCellVisibility

Signed-off-by: Chia-Ping Tsai <chia7712@gmail.com>

hbase-client/src/main/java/org/apache/hadoop/hbase/client/Mutation.java

@@ -331,7 +331,6 @@ public abstract class Mutation extends OperationWithAttributes implements Row, C
 
   /**
    * Sets the visibility expression associated with cells in this Mutation.
-   * It is illegal to set <code>CellVisibility</code> on <code>Delete</code> mutation.
    * @param expression
    */
   public Mutation setCellVisibility(CellVisibility expression) {