Find leaf sub-locations instead of all children

We will never do a put-away in an intermediate location,
so they should never be kept as candidate locations for the
put-away.

Follow the change in OCA#12

stock_storage_type_putaway_abc/models/stock_location.py

@@ -41,7 +41,7 @@ def get_storage_locations(self, products=None):
         return super().get_storage_locations(products)
 
     def _get_abc_locations(self, products):
-        return self.children_ids._sort_abc_locations(first(products).abc_storage)
+        return self.leaf_location_ids._sort_abc_locations(first(products).abc_storage)
 
     def _sort_abc_locations(self, product_abc):
         product_abc = product_abc or "a"