message: EnumsGen: remove dangling assertion
  StringAttr-backed enum attribute cases changed to allow explicit values,
  But this assertion was not deleted.
  Fixes
diff: @@ -149,7 +149,6 @@ StringRef tblgen::EnumAttrCase::getSymbol() const {
  }
  int64_t tblgen::EnumAttrCase::getValue() const {
  - assert(isStrCase() && "cannot get value for EnumAttrCase");
  return def->getValueAsInt("value");
  }
  