Fix icon when passing Marker to GeoJson (#2086)

* fix geojson marker icon

* mypy

* ruff

* After review comments

---------

Co-authored-by: Hans Then <hans.then@gmail.com>

Author: Conengmo

folium/map.py

@@ -403,8 +403,11 @@ def __init__(
         self.options = remove_empty(
             draggable=draggable or None, autoPan=draggable or None, **kwargs
         )
+        # this attribute is not used by Marker, but by GeoJson
+        self.icon = None
         if icon is not None:
             self.add_child(icon)
+            self.icon = icon
         if popup is not None:
             self.add_child(popup if isinstance(popup, Popup) else Popup(str(popup)))
         if tooltip is not None:
@@ -421,15 +424,12 @@ def _get_self_bounds(self) -> TypeBoundsReturn:
         return cast(TypeBoundsReturn, [self.location, self.location])
 
     def render(self):
-        from .features import CustomIcon, DivIcon
-
         if self.location is None:
             raise ValueError(
                 f"{self._name} location must be assigned when added directly to map."
             )
-        for child in list(self._children.values()):
-            if isinstance(child, (Icon, CustomIcon, DivIcon)):
-                self.add_child(self.SetIcon(marker=self, icon=child))
+        if self.icon:
+            self.add_child(self.SetIcon(marker=self, icon=self.icon))
         super().render()