DOC: update contextily example (#1088)
DOC: update contextily example (#1088)

* DOC: update contextily example

* Split optional/default

jorisvandenbossche/geopandas,jdmcbr/geopandas,jorisvandenbossche/geopandas,geopandas/geopandas,jdmcbr/geopandas,geopandas/geopandas,geopandas/geopandas,jorisvandenbossche/geopandas