Fix drawLineOverlay compile error

A cut-n-paste error from drawTextOverlay left drawLineOverlay.
This hasn't been tested since it wasn't possible that anyone
was successfully using this method. Corrected based on the docs:

```
In [10]: help(ImageDraw2.Draw.line)
Help on method line in module ImageDraw2:

line(self, xy, *options) unbound ImageDraw2.Draw method
```