[turbofan] Also update the BranchHint when merging a BooleanNot.

src/compiler/common-operator.h

Index: src/compiler/common-operator.h
diff --git a/src/compiler/common-operator.h b/src/compiler/common-operator.h
index 4d8b1694b1cb35e906f10be59e8cc3761befd3ed..3b89b2cd038431d26ff745c88ab3edeaa8affa68 100644
--- a/src/compiler/common-operator.h
+++ b/src/compiler/common-operator.h
@@ -27,6 +27,19 @@ class Operator;
 // Prediction hint for branches.
 enum class BranchHint : uint8_t { kNone, kTrue, kFalse };
 
+inline BranchHint NegateBranchHint(BranchHint hint) {
+  switch (hint) {
+    case BranchHint::kNone:
+      return hint;
+    case BranchHint::kTrue:
+      return BranchHint::kFalse;
+    case BranchHint::kFalse:
+      return BranchHint::kTrue;
+  }
+  UNREACHABLE();
+  return hint;
+}
+
 inline size_t hash_value(BranchHint hint) { return static_cast<size_t>(hint); }
 
 std::ostream& operator<<(std::ostream&, BranchHint);