infixScheduleMupa: drop work-around for bug in isl

The bug has been fixed.

Author: Sven Verdoolaege

tc/core/polyhedral/schedule_transforms.cc

@@ -459,8 +459,6 @@ isl::multi_union_pw_aff infixScheduleMupa(
   auto domain = domainElem->domain_.universe();
   auto zero = isl::multi_val::zero(domain.get_space().set_from_params());
   auto prefix = isl::multi_union_pw_aff(domain, zero);
-  // Work around bug in isl.
-  prefix = prefix.intersect_domain(domain);
   prefix = foldl(
       filterType<ScheduleTreeElemBand>(tree->ancestors(relativeRoot)),
       [](const ScheduleTree* st, isl::multi_union_pw_aff pref) {