Fix TopoJson non-collection geometries

[KhadeerBasha1232]

Fixes #1816

Problem

When a TopoJSON's objects entry had a type of Polygon or
MultiPolygon (instead of GeometryCollection), folium raised:

KeyError: 'geometries'

This happened because the code assumed every object had a geometries
key and didn't handle "bare" geometry objects that store their arcs
directly.

Fix

Updated the TopoJson handling in folium/features.py so it also
supports non-collection geometry types (Polygon, MultiPolygon,
etc.), not just GeometryCollection.

Testing

Reproduced the exact example from #1816 — it rendered without the
KeyError after this change. Ran the existing test suite locally with
python -m pytest tests --ignore=tests/selenium and all tests pass.

[KhadeerBasha1232]

This fixes #1816 — TopoJson raised a KeyError('geometries') when the
topology object's type was Polygon or MultiPolygon instead of
GeometryCollection, since the code assumed every object had a
geometries key.

Fix checks type first and falls back to treating the object itself
as a single-item geometry list when it's not a GeometryCollection.

Added a parametrized test covering both Polygon and MultiPolygon cases.
All existing tests + pre-commit checks pass locally. Happy to make any
changes if needed!