Update contains_tests.cpp to use public cudf::slice (#16253)

Changes the `cpp/tests/lists/contains_test.cpp` to use `cudf::slice` instead of `cudf::detail::slice()`

Authors:
  - David Wendt (https://github.com/davidwendt)

Approvers:
  - Robert Maynard (https://github.com/robertmaynard)
  - Bradley Dice (https://github.com/bdice)
  - Muhammad Haseeb (https://github.com/mhaseeb123)

URL: #16253

cpp/tests/lists/contains_tests.cpp

@@ -224,9 +224,8 @@ TYPED_TEST(TypedContainsTest, SlicedLists)
 
   {
     // First Slice.
-    auto sliced_column_1 =
-      cudf::detail::slice(search_space, {1, 8}, cudf::get_default_stream()).front();
-    auto search_key_one = create_scalar_search_key<T>(1);
+    auto sliced_column_1 = cudf::slice(search_space, {1, 8}, cudf::get_default_stream()).front();
+    auto search_key_one  = create_scalar_search_key<T>(1);
     {
       // CONTAINS
       auto result          = cudf::lists::contains(sliced_column_1, *search_key_one);
@@ -257,9 +256,8 @@ TYPED_TEST(TypedContainsTest, SlicedLists)
 
   {
     // Second Slice.
-    auto sliced_column_2 =
-      cudf::detail::slice(search_space, {3, 10}, cudf::get_default_stream()).front();
-    auto search_key_one = create_scalar_search_key<T>(1);
+    auto sliced_column_2 = cudf::slice(search_space, {3, 10}, cudf::get_default_stream()).front();
+    auto search_key_one  = create_scalar_search_key<T>(1);
     {
       // CONTAINS
       auto result          = cudf::lists::contains(sliced_column_2, *search_key_one);