[llvm] [ADT][NFC] Remove unused ValueInfoT from DenseSetImpl (PR #207277)

[Nikita Popov via llvm-commits]

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@@ -52,8 +52,7 @@ template <typename KeyT> class DenseSetPair : public DenseSetEmpty {
 ///
 /// or the equivalent SmallDenseMap type.  ValueInfoT must implement the
 /// DenseMapInfo "concept".
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nikic wrote:

```suggestion
/// or the equivalent SmallDenseMap type.
```

https://github.com/llvm/llvm-project/pull/207277