feat(mge): do not export F.nn.sync_batch_norm

GitOrigin-RevId: aa05e3aac4

imperative/python/megengine/functional/nn.py

@@ -57,7 +57,6 @@ __all__ = [
     "softmax",
     "softplus",
     "svd",
-    "sync_batch_norm",
     "warp_perspective",
 ]
 

imperative/python/megengine/module/batchnorm.py

@@ -11,7 +11,7 @@ from typing import Optional
 import numpy as np
 
 from ..distributed.group import WORLD, Group
-from ..functional import batch_norm2d, sync_batch_norm
+from ..functional.nn import batch_norm2d, sync_batch_norm
 from ..tensor import Parameter, Tensor
 from . import init
 from .module import Module