fix boxplot column misorder

Author: joyahuang

pandas/plotting/_matplotlib/boxplot.py

@@ -214,7 +214,7 @@ def _make_plot(self, fig: Figure) -> None:
                     # values, instead of label which is used as subtitle in this case.
                     # error: "Index" has no attribute "levels"; maybe "nlevels"?
                     levels = self.data.columns.levels  # type: ignore[attr-defined]
-                    ticklabels = [pprint_thing(col) for col in levels[0]]
+                    ticklabels = [pprint_thing(col) for col in self.data.columns.get_level_values(0)] # 
                 else:
                     ticklabels = [pprint_thing(label)]