Fix memset error in nvtext::edit_distance_matrix (#14283)

Fixes a bug in `nvtext::edit_distance_matrix` where the internal offsets vector is initialized to 0. 
This error was introduced in #13912 
The bug was found while working on a different PR which re-ordered the nvtext gtests execution causing device memory to be reused from the rmm pool in a different way.

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

Approvers:
  - Bradley Dice (https://github.com/bdice)
  - Mark Harris (https://github.com/harrism)
  - Nghia Truong (https://github.com/ttnghia)

URL: #14283

cpp/src/text/edit_distance.cu

@@ -224,7 +224,7 @@ std::unique_ptr<cudf::column> edit_distance_matrix(cudf::strings_column_view con
   cudf::size_type n_upper = (strings_count * (strings_count - 1)) / 2;
   rmm::device_uvector<std::ptrdiff_t> offsets(n_upper, stream);
   auto d_offsets = offsets.data();
-  CUDF_CUDA_TRY(cudaMemsetAsync(d_offsets, 0, n_upper * sizeof(cudf::size_type), stream.value()));
+  CUDF_CUDA_TRY(cudaMemsetAsync(d_offsets, 0, n_upper * sizeof(std::ptrdiff_t), stream.value()));
   thrust::for_each_n(
     rmm::exec_policy(stream),
     thrust::make_counting_iterator<cudf::size_type>(0),