[clang] [NFC][Diagnostics] Prevent incorrect clang-format reformatting in some headers related to Clang diagnostics (PR #154628)

[Dan Liew via cfe-commits]

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@@ -14,6 +14,7 @@
 #ifndef LLVM_CLANG_BASIC_ALLDIAGNOSTICS_H
 #define LLVM_CLANG_BASIC_ALLDIAGNOSTICS_H
 
+// clang-format off
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delcypher wrote:

I had assumed that the inclusion order was deliberate but taking a closer look I see it doesn't actually match the declaration order of the categories (i.e. `Common`, `Driver, `Frontend`...). I'll just reformat this bit.

https://github.com/llvm/llvm-project/pull/154628