Warning when specifying node colors

A minimal working example is
```python
import xgi
import random

H = xgi.Hypergraph([[1, 2], [2, 3, 4]])

c1 = "maroon"
c2 = "white"
node_fc = [c1 if random.random() < 0.5 else c2 for i in H.nodes]
xgi.draw(H, node_fc=node_fc)
```
produces this warning
```
UserWarning: No data for colormapping provided via 'c'. Parameters 'cmap' will be ignored
  node_collection = ax.scatter(
```