Update matplotlib.py to use .get_next_color

At some point between matplotlib 2.1 and 3.9, ax._get_lines.prop_cycler was removed. The recommended replacement (per https://stackoverflow.com/a/78938755) is to use ax._get_lines.get_next_color(). Implemented with a try/except to hopefully support both.

src/hapsira/plotting/orbit/backends/matplotlib.py

@@ -69,8 +69,12 @@ def _get_colors(self, color, trail):
 
         """
         if color is None:
-            # HACK: https://stackoverflow.com/a/13831816/554319
-            color = next(self.ax._get_lines.prop_cycler)["color"]
+            try:
+                # Updated HACK, see https://stackoverflow.com/a/78938755
+                color = ax._get_lines.get_next_color()
+            except AttributeError:
+                # HACK: https://stackoverflow.com/a/13831816/554319
+                color = next(self.ax._get_lines.prop_cycler)["color"]
 
         colors = [color, to_rgba(color, 0)] if trail else [color]
         return colors