Fix import in test

hopper/test_flash_attn.py

@@ -6,8 +6,7 @@ import torch.nn.functional as F
 
 from einops import rearrange, repeat
 from flash_attn_interface import flash_attn_func, flash_attn_varlen_func
-# from tests.test_util import generate_random_padding_mask, generate_qkv, construct_local_mask, attention_ref
-from test_util import generate_random_padding_mask, generate_qkv, construct_local_mask, attention_ref
+from tests.test_util import generate_random_padding_mask, generate_qkv, construct_local_mask, attention_ref
 
 ABS_TOL = 5e-3
 REL_TOL = 1e-1