Add missing @since for 7.6.2

Change-Id: I6f33dcdc4785b8e73f768abfe955fba178bd9c76

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

@@ -524,7 +524,7 @@ public class GridConnector extends AbstractHasComponentsConnector implements
          * Fetches id from the row object that corresponds with the given
          * rowIndex.
          * 
-         * @since
+         * @since 7.6.1
          * @param rowIndex
          *            the index of the row for which to fetch the id
          * @return id of the row if such id exists, {@code null} otherwise

client/src/com/vaadin/client/widget/grid/HeightAwareDetailsGenerator.java

@@ -22,7 +22,7 @@ package com.vaadin.client.widget.grid;
  * temporary workaround and might be removed or renamed at any time.
  * </p>
  * 
- * @since
+ * @since  7.6.1
  * @author Vaadin Ltd
  */
 @Deprecated
@@ -36,7 +36,7 @@ public interface HeightAwareDetailsGenerator extends DetailsGenerator {
      * temporary workaround and might be removed or renamed at any time.
      * </p>
      * 
-     * @since
+     * @since 7.6.1
      * @param rowIndex
      *            the index of the row for which to calculate details row height
      * @return height of the details row