Fix distribution of test data

This is not caught in CI, because test data is not distirbuted by
default, but it is downstream.

Author: QuLogic

setupext.py

@@ -495,12 +495,12 @@ def get_package_data(self):
                 'tests/test_*.ipynb',
             ],
             'mpl_toolkits': [
-                *_pkg_data_helper('mpl_toolkits/axes_grid1',
-                                  'tests/baseline_images'),
-                *_pkg_data_helper('mpl_toolkits/axisartist'
-                                  'tests/baseline_images'),
-                *_pkg_data_helper('mpl_toolkits/mplot3d'
-                                  'tests/baseline_images'),
+                *_pkg_data_helper('mpl_toolkits',
+                                  'axes_grid1/tests/baseline_images'),
+                *_pkg_data_helper('mpl_toolkits',
+                                  'axisartist/tests/baseline_images'),
+                *_pkg_data_helper('mpl_toolkits',
+                                  'mplot3d/tests/baseline_images'),
             ]
         }