message: remove unneded UNREACHABLE() stmts
diff: @@ -1144,7 +1144,6 @@ StateValue UnaryReductionOp::toSMT(State &s) const {
  case SMin: res.value = res.value.smin(ith.value); break;
  case UMax: res.value = res.value.umax(ith.value); break;
  case UMin: res.value = res.value.umin(ith.value); break;
  - default: UNREACHABLE();
  }
  // The result is non-poisonous if all lanes are non-poisonous.
  res.non_poison &= ith.non_poison;
  @@ -2305,7 +2304,6 @@ StateValue FCmp::toSMT(State &s) const {
  case TRUE: return expr(true);
  case FALSE: return expr(false);
  }
  - UNREACHABLE();
  };
  auto [val, np] = fm_poison(s, a.value, a.non_poison, b.value, b.non_poison,
  cmp, fmath, true);
  