layers: Update 'string' layer header files
Remove struct_string_helper header files, add in enum_string_helper
and <sstream> as these were included in the removed header file.
Change-Id: Ice0842ce2f06b5581a5add739534d59d834edbf6
diff --git a/layers/unique_objects.cpp b/layers/unique_objects.cpp
index bd9aabd..779693e 100644
--- a/layers/unique_objects.cpp
+++ b/layers/unique_objects.cpp
@@ -40,7 +40,7 @@
#include "vk_layer_table.h"
#include "vk_layer_utils.h"
#include "vk_layer_utils.h"
-#include "vk_struct_string_helper_cpp.h"
+#include "vk_enum_string_helper.h"
#include "vk_validation_error_messages.h"
#include "vulkan/vk_layer.h"