Fix Debug build break with device_uvectors in grouped_rolling.cu (#7633)

After #7523, on `Debug` builds, one seems to see the following build error:
```
cudf/cpp/src/rolling/grouped_rolling.cu(130): error: no operator "[]" matches these operands
            operand types are: const cudf::groupby::detail::sort::sort_groupby_helper::index_vector [ int ]
...
cudf/cpp/src/rolling/grouped_rolling.cu(130): error: no operator "[]" matches these operands
            operand types are: const cudf::groupby::detail::sort::sort_groupby_helper::index_vector [ unsigned long ] 
```

The offending line has an `assert()` that is only compiled during `Debug` builds. This commit corrects the indexing into `device_uvector`.

Authors:
  - MithunR (@mythrocks)

Approvers:
  - David (@davidwendt)
  - Nghia Truong (@ttnghia)
  - Devavret Makkar (@devavret)
  - Karthikeyan (@karthikeyann)

URL: #7633

cpp/src/rolling/grouped_rolling.cu

@@ -110,8 +110,8 @@ std::unique_ptr<column> grouped_rolling_window(table_view const& group_keys,
   using sort_groupby_helper = cudf::groupby::detail::sort::sort_groupby_helper;
 
   sort_groupby_helper helper{group_keys, cudf::null_policy::INCLUDE, cudf::sorted::YES};
-  auto const& group_offsets{helper.group_offsets()};
-  auto const& group_labels{helper.group_labels()};
+  auto const& group_offsets{helper.group_offsets(stream)};
+  auto const& group_labels{helper.group_labels(stream)};
 
   // `group_offsets` are interpreted in adjacent pairs, each pair representing the offsets
   // of the first, and one past the last elements in a group.
@@ -127,8 +127,8 @@ std::unique_ptr<column> grouped_rolling_window(table_view const& group_keys,
   //   groups.)
   //   3. [0, 500, 1000] indicates two equal-sized groups: [0,500), and [500,1000).
 
-  assert(group_offsets.size() >= 2 && group_offsets[0] == 0 &&
-         group_offsets[group_offsets.size() - 1] == input.size() &&
+  assert(group_offsets.size() >= 2 && group_offsets.element(0, stream) == 0 &&
+         group_offsets.element(group_offsets.size() - 1, stream) == input.size() &&
          "Must have at least one group.");
 
   auto preceding_calculator = [d_group_offsets = group_offsets.data(),