del the DEFINE_ALIAS of sigmoid_cross_entropy_with_logits (#27883)

* del the DEFINE_ALIAS of sigmoid_cross_entropy_with_logits

* del sigmoid_cross_entropy_with_logits in python/paddle/nn/functional/loss.py, test=develop

* call paddle.fluid.layers.sigmoid_cross_entropy_with_logits in bce_with_logits_loss, test=develop

python/paddle/nn/functional/__init__.py

@@ -143,7 +143,6 @@ from .loss import nll_loss  #DEFINE_ALIAS
 from .loss import npair_loss  #DEFINE_ALIAS
 from .loss import rank_loss  #DEFINE_ALIAS
 from .loss import sampled_softmax_with_cross_entropy  #DEFINE_ALIAS
-from .loss import sigmoid_cross_entropy_with_logits  #DEFINE_ALIAS
 from .loss import sigmoid_focal_loss  #DEFINE_ALIAS
 from .loss import smooth_l1  #DEFINE_ALIAS
 from .loss import smooth_l1_loss  #DEFINE_ALIAS

python/paddle/nn/functional/loss.py

@@ -31,7 +31,6 @@ from ...fluid.layers import log_loss  #DEFINE_ALIAS
 from ...fluid.layers import npair_loss  #DEFINE_ALIAS
 from ...fluid.layers import rank_loss  #DEFINE_ALIAS
 from ...fluid.layers import reshape
-from ...fluid.layers import sigmoid_cross_entropy_with_logits  #DEFINE_ALIAS
 from ...fluid.layers import smooth_l1  #DEFINE_ALIAS
 from ...fluid.layers import softmax_with_cross_entropy  #DEFINE_ALIAS
 from ...fluid.layers import square_error_cost  #DEFINE_ALIAS
@@ -66,7 +65,6 @@ __all__ = [
     'npair_loss',
     'rank_loss',
     'sampled_softmax_with_cross_entropy',
-    'sigmoid_cross_entropy_with_logits',
     'sigmoid_focal_loss',
     'smooth_l1',
     'smooth_l1_loss',
@@ -316,7 +314,7 @@ def binary_cross_entropy_with_logits(logit,
     if reduction == 'none' and pos_weight is None and weight is None:
         sigmoid_name = name
 
-    out = paddle.nn.functional.sigmoid_cross_entropy_with_logits(
+    out = paddle.fluid.layers.sigmoid_cross_entropy_with_logits(
         logit, label, name=sigmoid_name)
 
     one = paddle.fill_constant(shape=[1], value=1.0, dtype=logit.dtype)