clean up compiler warning

Signed-off-by: mloufra <mloufra@amazon.com>

src/main/java/org/opensearch/sdk/TransportActions.java

@@ -26,7 +26,7 @@
  */
 public class TransportActions {
     private final Logger logger = LogManager.getLogger(TransportActions.class);
-    private Map<String, Class> transportActions;
+    private Map<String, Class<?>> transportActions;
 
     /**
      * Constructor for TransportActions. Creates a map of transportActions for this extension.