[NFC] Removed unused member from HeapTypeGenerator (#7680)

Author: tlively

src/tools/fuzzing/heap-types.cpp

@@ -57,9 +57,7 @@ struct HeapTypeGeneratorImpl {
   FuzzParams params;
 
   HeapTypeGeneratorImpl(Random& rand, FeatureSet features, size_t n)
-    : result{TypeBuilder(n),
-             std::vector<std::vector<Index>>(n),
-             std::vector<std::optional<Index>>(n)},
+    : result{TypeBuilder(n), std::vector<std::vector<Index>>(n)},
       builder(result.builder), subtypeIndices(result.subtypeIndices),
       supertypeIndices(n), rand(rand), features(features) {
     // Set up the subtype relationships. Start with some number of root types,

src/tools/fuzzing/heap-types.h

@@ -32,9 +32,6 @@ struct HeapTypeGenerator {
   // The intended subtypes of each built type.
   std::vector<std::vector<Index>> subtypeIndices;
 
-  // The intended supertype of each built type, if any.
-  std::vector<std::optional<Index>> supertypeIndices;
-
   // Create a populated `HeapTypeGenerator` with `n` random HeapTypes with
   // interesting subtyping.
   static HeapTypeGenerator create(Random& rand, FeatureSet features, size_t n);