message: removes sync from `toc` call
diff: @@ -272,7 +272,6 @@ protected:
  double toc_impl() override
  {
  - exec_->synchronize();
  gko::cuda::device_guard g{id_};
  // Currently, gko::CudaExecutor always use default stream.
  GKO_ASSERT_NO_CUDA_ERRORS(cudaEventRecord(stop_));
  @@ -340,7 +339,6 @@ protected:
  double toc_impl() override
  {
  - exec_->synchronize();
  gko::hip::device_guard g{id_};
  // Currently, gko::HipExecutor always use default stream.
  GKO_ASSERT_NO_HIP_ERRORS(hipEventRecord(stop_));
  