Actually run op_linear_test in OSS (#8238)

I forgot to add it to CMakeLists.txt when I added it.

Author: swolchok

kernels/test/CMakeLists.txt

@@ -268,6 +268,7 @@ set(_optimized_kernels_test_sources
     "op_fft_r2c_test.cpp"
     "op_gelu_test.cpp"
     "op_le_test.cpp"
+    "op_linear_test.cpp"
     "op_log_softmax_test.cpp"
     "op_mul_test.cpp"
     "op_native_layer_norm_test.cpp"