fix github issue 15267 test=develop (#15306)

* fix github issue 15267 test=develop

* fix github issue 15267 test=develop

python/paddle/fluid/layers/nn.py

@@ -8479,8 +8479,7 @@ def shape(input):
     """
 
     helper = LayerHelper('shape', **locals())
-    out = helper.create_variable_for_type_inference(
-        dtype=helper.input_dtype('input'))
+    out = helper.create_variable_for_type_inference(dtype='int32')
     helper.append_op(
         type='shape', inputs={'Input': input}, outputs={'Out': out})