text: Title: ENH: Improve error message for attempting to write multiple geometry columns using `to_file`
  Body: xref #2565
  
  ```python
  In [16]: gdf = gpd.GeoDataFrame({"a":[1,2]}, geometry=[Point(1,1), Point(1,2)])
  
  In [17]: gdf['geom2'] = gdf.geometry
  
  In [18]: gdf.to_file("tmp.gpkg")
  -----------------------------------
  File ...\venv\lib\site-packages\geopandas\io\file.py:596, in infer_schema.<locals>.convert_type(column, in_type)
      594     out_type = types[str(in_type)]
      595 else:
  --> 596     out_type = type(np.zeros(1, in_type).item()).__name__
      597 if out_type == "long":
      598     out_type = "int"
  
  TypeError: Cannot interpret '<geopandas.array.GeometryDtype object at 0x0000025FA88908E0>' as a data type
  
  ```
  
  