[Polly] Use isl::set::tuple_dim instead of isl::set::dim. NFC

This is part of an effort to reduce the differences between the custom C++ bindings used right now by polly in `lib/External/isl/include/isl/isl-noxceptions.h` and the official isl C++ interface.

Note that not all the usages of `isl::set::dim` were replaced

GitOrigin-RevId: 159e072f812317c26d480d79408b6606b010d800
diff --git a/lib/Analysis/DependenceInfo.cpp b/lib/Analysis/DependenceInfo.cpp
index 7c492ba..6a2e2c0 100644
--- a/lib/Analysis/DependenceInfo.cpp
+++ b/lib/Analysis/DependenceInfo.cpp
@@ -667,7 +667,7 @@
   Dependences = Dependences.apply_range(Schedule);
 
   isl::set Zero = isl::set::universe(ScheduleSpace);
-  for (auto i : seq<isl_size>(0, Zero.dim(isl::dim::set)))
+  for (auto i : seq<isl_size>(0, Zero.tuple_dim()))
     Zero = Zero.fix_si(isl::dim::set, i, 0);
 
   isl::union_set UDeltas = Dependences.deltas();