Fix tense in docstring

Author: andylolz

flattentool/sort_iati.py

@@ -108,7 +108,7 @@ def element_loop(self, element, path):
 
     def create_schema_dict(self, parent_name, parent_element=None):
         """
-        Created a nested OrderedDict representing the structure (and order!) of
+        Create a nested OrderedDict representing the structure (and order!) of
         elements in the IATI schema.
         """
         if parent_element is None: