[clang] [ASTMatcher] Fix redundant macro expansion checks in getExpansionLocOfMacro (PR #117143)

[Aaron Ballman via cfe-commits]

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@@ -36,6 +36,7 @@
 #include <cstddef>
 #include <optional>
 #include <string>
+#include <unordered_set>
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AaronBallman wrote:

Would `llvm::DenseSet` make more sense?

https://llvm.org/docs/ProgrammersManual.html#llvm-adt-denseset-h

https://github.com/llvm/llvm-project/pull/117143