mpl: replace deprecated all_backends

Author: mathause

mplotutils/tests/test_get_renderer.py

@@ -6,7 +6,7 @@
 from . import figure_context, restore_backend
 
 
-@pytest.mark.parametrize("backend", matplotlib.rcsetup.all_backends)
+@pytest.mark.parametrize("backend", matplotlib.backends.backend_registry.list_builtin())
 def test_get_renderer(backend):
 
     with restore_backend(backend):