Fix alignment on "Seats" and "Price" columns

Bad column keys where being used on `setColumnAlignment` for `seats` and `price` columns.

Author: juanghurtado

src/main/java/com/vaadin/demo/dashboard/view/transactions/TransactionsView.java

@@ -207,8 +207,8 @@ protected String formatPropertyValue(final Object rowId,
         table.setSortContainerPropertyId("time");
         table.setSortAscending(false);
 
-        table.setColumnAlignment("Seats", Align.RIGHT);
-        table.setColumnAlignment("Price", Align.RIGHT);
+        table.setColumnAlignment("seats", Align.RIGHT);
+        table.setColumnAlignment("price", Align.RIGHT);
 
         table.setVisibleColumns("time", "country", "city", "theater", "room",
                 "title", "seats", "price");