indicate that stamen tiles require a stadia account (#1226)

examples/user_guide/Geographic_Data.ipynb

@@ -24,7 +24,7 @@
     "\n",
     "    conda install geoviews\n",
     "    \n",
-    "or if the cartopy dependency has been satisfied in some other way, GeoViews may also be installed using pip:\n",
+    "or with pip:\n",
     "\n",
     "    pip install geoviews\n",
     "\n",
@@ -265,7 +265,7 @@
     "- ``global_extent`` (default=False): Whether to expand the plot extent to span the whole globe\n",
     "- ``project`` (default=False): Whether to project the data before plotting (adds initial overhead but avoids projecting data when plot is dynamically updated)\n",
     "- ``tiles`` (default=False): Whether to overlay the plot on a tile source. Tiles sources can be selected by name, the default is 'Wikipedia'.\n",
-    "Other options are: 'CartoDark', 'CartoEco', 'CartoLight', 'CartoMidnight', 'EsriImagery', 'EsriNatGeo', 'EsriReference''EsriTerrain', 'EsriUSATopo', 'OSM', 'StamenLabels', 'StamenTerrain', 'StamenTerrainRetina', 'StamenToner', 'StamenTonerBackground', 'StamenWatercolor'"
+    "Other options are: 'CartoDark', 'CartoEco', 'CartoLight', 'CartoMidnight', 'EsriImagery', 'EsriNatGeo', 'EsriReference''EsriTerrain', 'EsriUSATopo', 'OSM', 'StamenLabels', 'StamenTerrain', 'StamenTerrainRetina', 'StamenToner', 'StamenTonerBackground', 'StamenWatercolor'. Stamen tile sources require a Stadia account when not running locally; see [stadiamaps.com](https://stadiamaps.com/)."
    ]
   }
  ],