Remove logger from layernorm (#332)

Upstream does not use logger in layernorm. Neither do we. No idea why
it's there.

vllm/model_executor/layers/layernorm.py

@@ -4,11 +4,8 @@
 import torch
 import torch.nn as nn
 
-from vllm.logger import init_logger
 from vllm.model_executor.custom_op import CustomOp
 
-logger = init_logger(__name__)
-
 
 class RMSNorm(CustomOp):
  """Root mean square normalization.