Fixing the PK of igTreeGrid sample

Author: mpavlinov

samples/igTreeGrid.html

@@ -54,7 +54,7 @@ <h1 class="push-down-md"><a href="http://igniteui.com/tree-grid/overview" target
                               data-source="tasks"
                               width="100%"
                               height="400px"
-                              primary-key="ProductID"
+                              primary-key="id"
                               auto-commit="true"
                               auto-generate-columns="false"
                               child-data-key="products"

src-samples/src/igTreeGrid.html

@@ -22,7 +22,7 @@ <h1 class="push-down-md"><a href="http://igniteui.com/tree-grid/overview" target
                               data-source="tasks"
                               width="100%"
                               height="400px"
-                              primary-key="ProductID"
+                              primary-key="id"
                               auto-commit="true"
                               auto-generate-columns="false"
                               child-data-key="products"