fix import

Author: wpbonelli

autotest/test_dfns.py

@@ -4,7 +4,7 @@
 import pytest
 from packaging.version import Version
 
-from modflow_devtools.dfn2toml import convert, is_valid
+from modflow_devtools.dfns.dfn2toml import convert, is_valid
 from modflow_devtools.dfns import Dfn, _load_common, load, load_flat
 from modflow_devtools.dfns.fetch import fetch_dfns
 from modflow_devtools.dfns.schema.v1 import FieldV1