[llvm] [IR] Modernize StructuralHashImpl (NFC) (PR #105951)

[Aiden Grossman via llvm-commits]

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@@ -43,7 +43,7 @@ class StructuralHashImpl {
   }
 
 public:
-  StructuralHashImpl() : Hash(4) {}
+  StructuralHashImpl() = default;
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boomanaiden154 wrote:

What's the reason for marking the constructor as default here instead of just omitting it?

https://github.com/llvm/llvm-project/pull/105951