[caffe2] fix how np.clip is used in lengths_reducer_fused_{4,8}_rowwise_ops_test (#32086)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/32086
np.clip(1, num_indices // 2, 10) -> np.clip(num_indices // 2, 1, 10)
Also change batchsize -> num_rows to match with what the variable actually does
Test Plan: CI
Reviewed By: hx89
Differential Revision: D19361521
fbshipit-source-id: 9ce864c7d7da046dc606afa5207da677ccf80f52
