Remove unnecessary sentinel node in coo tensors while filling row pointers.

PiperOrigin-RevId: 762458372

Author: manuadg-verily

jax_tpu_embedding/sparsecore/lib/core/input_preprocessing.cc

@@ -329,9 +329,6 @@ void PreprocessInputForStackedTablePerLocalDevice(
           stacked_table_name, allow_id_dropping, num_sc_per_device,
           total_num_coo_tensors, total_max_ids_per_sc,
           total_max_unique_ids_per_sc, required_buffer_size_per_sc);
-  for (int i = 0; i < num_sc_per_device; ++i) {
-    coo_tensors_by_id[i].emplace_back(batch_size_per_sc * (i + 1), 0, 0.0);
-  }
   //
   // Step 3: Compute the row pointers for each group of IDs.
   //