HBASE-22823 Mark Canary as Public/Evolving

Signed-off-by: Xu Cang <xucang@apache.org>

Author: Caroline Zhou

hbase-server/src/main/java/org/apache/hadoop/hbase/tool/Canary.java

@@ -119,7 +119,7 @@
  * </li>
  * </ol>
  */
-@InterfaceAudience.Private
+@InterfaceAudience.Public
 public final class Canary implements Tool {
   /**
    * Sink interface used by the canary to output information