[xla:cpu] scatter_benchmark: remove unique_indices=true

It's not clear to me that the update slices cannot overlap, regardless
of parameter values. (If they were simple scatters I'd easily
reason about this, but alas, they're not). Remove the flags then.

PiperOrigin-RevId: 716233312

xla/backends/cpu/benchmarks/scatter_benchmark_test.cc

@@ -35,7 +35,7 @@ namespace xla::cpu {
 namespace {
 
 // Generate random indices to be used in the scatter.
-// They must be unique so we randomly select from the range [0, slice_size)
+// To make them unique, we randomly select from the range [0, slice_size)
 // by first shuffling the full range and then taking the first slice_size
 // elements
 Literal createR1ScatterIndices(int64_t domain_size, int64_t scatter_size,
@@ -77,8 +77,7 @@ void BM_ScatterS32_R1(benchmark::State& state) {
           update_window_dims={},
           inserted_window_dims={0},
           scatter_dims_to_operand_dims={0},
-          index_vector_dim=1,
-          unique_indices=true
+          index_vector_dim=1
     }
     )";
 
@@ -125,8 +124,7 @@ void BM_ScatterS32_R2(benchmark::State& state) {
           update_window_dims={1},
           inserted_window_dims={0},
           scatter_dims_to_operand_dims={0},
-          index_vector_dim=1,
-          unique_indices=true
+          index_vector_dim=1
     }
     )";
 
@@ -172,8 +170,7 @@ void BM_ScatterS32_R3(benchmark::State& state) {
           update_window_dims={1, 2},
           inserted_window_dims={0},
           scatter_dims_to_operand_dims={0},
-          index_vector_dim=1,
-          unique_indices=true
+          index_vector_dim=1
     }
     )";