Remove unused raft cagra header in add_nodes.cuh (rapidsai#741)

Vector search headers in raft will be removed in the future, so we should not include the raft cagra header.

Authors:
  - Yinzuo Jiang (https://github.com/jiangyinzuo)
  - Corey J. Nolet (https://github.com/cjnolet)

Approvers:
  - Corey J. Nolet (https://github.com/cjnolet)

URL: rapidsai#741

Author: jiangyinzuo

cpp/src/neighbors/detail/cagra/add_nodes.cuh

@@ -19,7 +19,6 @@
 #include <raft/core/mdspan_types.hpp>
 #include <raft/core/resource/cuda_stream.hpp>
 #include <raft/core/resources.hpp>
-#include <raft/neighbors/cagra_types.hpp>
 #include <raft/spatial/knn/detail/ann_utils.cuh>
 #include <raft/stats/histogram.cuh>