Accomodate hull alternative visual for 2-point clusters

[patcon]

This error gets generated by QHull/scipy if trying to draw hull for less than 3 points. I've update code to skip 2-point hulls, so error won't show up.

[/usr/local/lib/python3.11/dist-packages/reddwarf/polis_pandas.py](https://localhost:8080/#) in generate_figure(self, coord_dataframe, labels)
    240                 if len(points) < 2:
    241                     continue
--> 242                 hull = ConvexHull(points)
    243                 hull_points = points.iloc[hull.vertices, :]
    244                 polygon = patches.Polygon(

_qhull.pyx in scipy.spatial._qhull.ConvexHull.__init__()

_qhull.pyx in scipy.spatial._qhull._Qhull.__init__()

QhullError: QH6214 qhull input error: not enough points(2) to construct initial simplex (need 3)

While executing:  | qhull i Qt
Options selected for Qhull 2019.1.r 2019/06/21:
  run-id 909967059  incidence  Qtriangulate  _pre-merge  _zero-centrum
  _maxoutside  0

Polis platform seems to avoid singleton 1-point clusters, but 2 can appear, and still need a visual to connect them.