layers: Move U_O:DestroySwapchain out of codegen

This function in the unique_objects layer will need to clean up some
swapchain image index tracking information and so will now be
manually written.

Change-Id: I306fdd9f7a3c75c21b82fe21951804bd86259781
diff --git a/scripts/unique_objects_generator.py b/scripts/unique_objects_generator.py
index 833207e..fe7cc9c 100644
--- a/scripts/unique_objects_generator.py
+++ b/scripts/unique_objects_generator.py
@@ -137,6 +137,7 @@
             'vkCreateSwapchainKHR',
             'vkCreateSharedSwapchainsKHR',
             'vkGetSwapchainImagesKHR',
+            'vkDestroySwapchainKHR',
             'vkQueuePresentKHR',
             'vkEnumerateInstanceLayerProperties',
             'vkEnumerateDeviceLayerProperties',