Set @since tags to 7.4

Change-Id: Icd51c52d2c93b71d25b938d03c827b2da5d8527c

client/src/com/vaadin/client/VLoadingIndicator.java

@@ -157,7 +157,7 @@ public class VLoadingIndicator {
      * Triggers displaying of this loading indicator unless it's already visible
      * or scheduled to be shown after a delay.
      * 
-     * @since
+     * @since 7.4
      */
     public void ensureTriggered() {
         if (!isVisible() && !firstTimer.isRunning()) {

client/src/com/vaadin/client/connectors/JavaScriptRendererConnector.java

@@ -39,7 +39,7 @@ import elemental.json.JsonValue;
 /**
  * Connector for server-side renderer implemented using JavaScript.
  * 
- * @since
+ * @since 7.4
  * @author Vaadin Ltd
  */
 @Connect(AbstractJavaScriptRenderer.class)

server/src/com/vaadin/ui/renderer/AbstractJavaScriptRenderer.java

@@ -99,7 +99,7 @@ import com.vaadin.ui.JavaScriptFunction;
  * </ul>
  * 
  * @author Vaadin Ltd
- * @since
+ * @since 7.4
  */
 public abstract class AbstractJavaScriptRenderer<T> extends AbstractRenderer<T> {
     private JavaScriptCallbackHelper callbackHelper = new JavaScriptCallbackHelper(

shared/src/com/vaadin/shared/annotations/NoLoadingIndicator.java

@@ -25,7 +25,7 @@ import java.lang.annotation.Target;
  * sending requests for RPC methods that are not marked with this annotation.
  * The loading indicator is hidden once a response is received.
  * 
- * @since
+ * @since 7.4
  * @author Vaadin Ltd
  */
 @Target(ElementType.METHOD)