tests: Fix object leak in AllocDescriptorFromEmptyPool

This fix allows run_wrap_objects_tests.sh to pass.
diff --git a/tests/layer_validation_tests.cpp b/tests/layer_validation_tests.cpp
index d962564..abf2e8a 100644
--- a/tests/layer_validation_tests.cpp
+++ b/tests/layer_validation_tests.cpp
@@ -3719,6 +3719,7 @@
 
     m_errorMonitor->VerifyFound();
 
+    vkDestroyDescriptorSetLayout(m_device->device(), ds_layout_samp, NULL);
     vkDestroyDescriptorSetLayout(m_device->device(), ds_layout_ub, NULL);
     vkDestroyDescriptorPool(m_device->device(), ds_pool, NULL);
 }