[clang] [clang-tools-extra] Fix OOM in FormatDiagnostic (PR #108187)

[Vakhurin Sergei via cfe-commits]

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@@ -571,8 +571,7 @@ DiagnosticIDs::getDiagnosticSeverity(unsigned DiagID, SourceLocation Loc,
   }
 
   // If explicitly requested, map fatal errors to errors.
-  if (Result == diag::Severity::Fatal &&
-      Diag.CurDiagID != diag::fatal_too_many_errors && Diag.FatalsAsError)
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igelbox wrote:

I'm not sure why do we checked for `Diag.CurDiagID != diag::fatal_too_many_errors` here.
Moreover even without this piece of code unit-tests succeed.

https://github.com/llvm/llvm-project/pull/108187