external: regenerate Vulkan headers.

src/MagnumExternal/Vulkan/flextVk.h

@@ -324,7 +324,7 @@ extern "C" {
 // Vulkan 1.2 version number
 #define VK_API_VERSION_1_2 VK_MAKE_VERSION(1, 2, 0)// Patch version should always be set to 0
 // Version of this file
-#define VK_HEADER_VERSION 166
+#define VK_HEADER_VERSION 168
 // Complete version of this file
 #define VK_HEADER_VERSION_COMPLETE VK_MAKE_VERSION(1, 2, VK_HEADER_VERSION)
 #define VK_DEFINE_HANDLE(object) typedef struct object##_T* object;