fix sanity error

Author: JiangZhaoh

python/mxnet/ndarray/numpy/_op.py

@@ -2969,7 +2969,7 @@ def append(arr, values, axis=None):
     array([1., 2., 3., 4., 5., 6., 7., 8., 9.])
 
     When `axis` is specified, `values` must have the correct shape.
-    
+
     >>> np.append(np.array([[1, 2, 3], [4, 5, 6]]), np.array([[7, 8, 9]]), axis=0)
     array([[1., 2., 3.],
            [4., 5., 6.],

python/mxnet/numpy/multiarray.py

@@ -4833,7 +4833,7 @@ def append(arr, values, axis=None):
     array([1., 2., 3., 4., 5., 6., 7., 8., 9.])
 
     When `axis` is specified, `values` must have the correct shape.
-    
+
     >>> np.append(np.array([[1, 2, 3], [4, 5, 6]]), np.array([[7, 8, 9]]), axis=0)
     array([[1., 2., 3.],
            [4., 5., 6.],

python/mxnet/symbol/numpy/_symbol.py

@@ -3059,7 +3059,7 @@ def append(arr, values, axis=None):
     array([1., 2., 3., 4., 5., 6., 7., 8., 9.])
 
     When `axis` is specified, `values` must have the correct shape.
-    
+
     >>> np.append(np.array([[1, 2, 3], [4, 5, 6]]), np.array([[7, 8, 9]]), axis=0)
     array([[1., 2., 3.],
            [4., 5., 6.],