Fix or mitigate #2152. CustomIcon doesn't exist (anymore?) in leaflet

Author: sgrefen

folium/features.py

@@ -1940,7 +1940,7 @@ def __init__(
         popup_anchor: Optional[Tuple[int, int]] = None,
     ):
         super(Icon, self).__init__()
-        self._name = "CustomIcon"
+        self._name = "icon"
         self.options = remove_empty(
             icon_url=image_to_url(icon_image),
             icon_size=icon_size,