removed unnecessary cell in doc file

Author: RenaudLN

doc/python/hexbin-mapbox.md

@@ -163,7 +163,3 @@ fig.show()
 #### Reference
 
 For more info on Plotly maps, see: https://plotly.com/python/maps.<br> For more info on using colorscales with Plotly see: https://plotly.com/python/heatmap-and-contour-colorscales/ <br>For more info on `ff.create_annotated_heatmap()`, see the [full function reference](https://plotly.com/python-api-reference/generated/plotly.figure_factory.create_hexbin_mapbox.html#plotly.figure_factory.create_hexbin_mapbox)
-
-```python
-
-```