minor: Rename function

Author: abawchen

graphene_mongo/converter.py

@@ -67,7 +67,7 @@ def convert_field_to_float(field, registry=None):
 
 @convert_mongoengine_field.register(mongoengine.DictField)
 @convert_mongoengine_field.register(mongoengine.MapField)
-def convert_dict_to_jsonstring(field, registry=None):
+def convert_field_to_jsonstring(field, registry=None):
     return JSONString(description=get_field_description(field, registry), required=field.required)