Use format specifier PRIu64 only with uint64_t types

Fixed: #399
diff --git a/include/vk_mem_alloc.h b/include/vk_mem_alloc.h
index 6a51339..34b83bf 100644
--- a/include/vk_mem_alloc.h
+++ b/include/vk_mem_alloc.h
@@ -3042,7 +3042,7 @@
     }
     static inline void VmaUint64ToStr(char* VMA_NOT_NULL outStr, size_t strLen, uint64_t num)
     {
-        snprintf(outStr, strLen, "%" PRIu64, static_cast<unsigned long long>(num));
+        snprintf(outStr, strLen, "%" PRIu64, num);
     }
     static inline void VmaPtrToStr(char* VMA_NOT_NULL outStr, size_t strLen, const void* ptr)
     {