[libcxx] [llvm] [libc++] Deprecate and remove meaningless `<cxxx>` headers (PR #111615)

[A. Jiang via llvm-commits]

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@@ -0,0 +1,42 @@
+// -*- C++ -*-
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frederick-vs-ja wrote:

Seems needed to make CI pass.

https://github.com/llvm/llvm-project/pull/111615