cmake is missing sparse/gram.cu gtest (rapidsai#1611)

The sparse/gram apis were moved from raft in rapidsai#463.
However, the cmake has not been updated to compile the tests.

Authors:
  - Anupam (https://github.com/aamijar)

Approvers:
  - Robert Maynard (https://github.com/robertmaynard)

URL: rapidsai#1611

Author: aamijar

cpp/tests/CMakeLists.txt

@@ -309,6 +309,7 @@ ConfigureTest(
        distance/gram.cu
        distance/masked_nn.cu
        distance/sparse_distance.cu
+       sparse/gram.cu
        sparse/neighbors/cross_component_nn.cu
   GPUS 1
   PERCENT 100