C10_UNUSED to [[maybe_unused]] (#6357)

Summary:
X-link: pytorch/pytorch#138364

Pull Request resolved: #6357

Reviewed By: dmm-fb

Differential Revision: D64613643

fbshipit-source-id: 8c0608376e5b21d9d3291bef6ae75e7d826d86bb

Author: r-barnes

backends/vulkan/runtime/utils/MacroUtils.h

@@ -8,7 +8,7 @@
 
 #pragma once
 
-// Suppress an unused variable. Copied from C10_UNUSED
+// Suppress an unused variable. Copied from [[maybe_unused]]
 #if defined(_MSC_VER) && !defined(__clang__)
 #define VK_UNUSED __pragma(warning(suppress : 4100 4101))
 #else