[clang] [clang][Sema] Accept gnu format attributes (PR #160255)

[Shafik Yaghmour via cfe-commits]

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@@ -503,7 +503,6 @@ enum class FormatStringType {
   FreeBSDKPrintf,
   OSTrace,
   OSLog,
-  Syslog,
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shafik wrote:

This change is not really explained. It feels like a drive by fix, which we usually discourage.

https://github.com/llvm/llvm-project/pull/160255