Update json.py

BUG : read_json with table='orient' causes unexpected type coercion pandas-dev#21345

Author: uds5501

pandas/io/json/json.py

@@ -711,7 +711,7 @@ def _try_convert_data(self, name, data, use_dtypes=True,
 
             # coerce ints if we can
             try:
-                new_data = data.astype('int64')
+                new_data = data.astype('float64')
                 if (new_data == data).all():
                     data = new_data
                     result = True