title: Altair not rendering mark_geoshape
body: <p>I have a geodataframe of 3 isochrone polygons that I am trying to visualize in Altair. The data loads fine in QGIS and Matplotlib but doesn't seem to render properly in Altair. For reference, the CRS is set to 4326.</p>
  <pre><code>gdf = gpd.read_file('https://brown-institute-assets.s3.us-east-1.amazonaws.com/Objects/pointsunknown/2021_Summer/Data/output-test.geojson')
  
  gdf = gdf.to_crs('EPSG:4326')
  
  alt.Chart(gdf).mark_geoshape()
  </code></pre>
  <p>In Altair, the result is this:</p>
  <p><a href="https://i.stack.imgur.com/7iVGC.png" rel="nofollow noreferrer">altair error</a></p>