message: remove implementation of may_have_escaped for BlamingStore
  Summary:
  It was not correct, and that wasn't obvious because it isn't being used.
  Better to remove it and add it back properly, when it can be tested.
diff: @@ -111,8 +111,9 @@ class BlameStore {
  dom->set(ptr, allocated());
  }
  - static bool may_have_escaped(const Domain& dom, const IRInstruction* ptr) {
  - return !dom.get(ptr).is_bottom();
  + static bool may_have_escaped(const Domain&, const IRInstruction*) {
  + // Unimplemented
  + not_reached();
  }
  static Value unallocated() { return Value::lifted(BlameDomain::bottom()); }
  