Update latlonutils.py

To avoid FutureWarning, Function "Iterable" should import from collections.abc.

src/wrf/latlonutils.py

@@ -1,6 +1,6 @@
 from __future__ import (absolute_import, division, print_function)
 
-from collections import Iterable
+from collections.abc import Iterable
 
 import numpy as np