Update typing hint for WCOSS version of python (NOAA-EMC#2238)

The typing hint `typing.List` was deprecated with python 3.9 in favor
of using the primitive `list[str]`, but the functional version of python
on WCOSS2 is <3.9, causing `setup_xml.py` to fail there. This replaces
`list[str]` as a typing hint with the deprecated form until the supported
version on WCOSS2 is >=3.9.

Author: KateFriedman-NOAA

workflow/rocoto/tasks.py

@@ -4,6 +4,7 @@
 from applications.applications import AppConfig
 import rocoto.rocoto as rocoto
 from wxflow import Template, TemplateConstants, to_timedelta
+from typing import List
 
 __all__ = ['Tasks']
 
@@ -124,7 +125,7 @@ def _template_to_rocoto_cycstring(self, template: str, subs_dict: dict = {}) ->
                                              rocoto_conversion_dict.get)
 
     @staticmethod
-    def _get_forecast_hours(cdump, config) -> list[str]:
+    def _get_forecast_hours(cdump, config) -> List[str]:
         fhmin = config['FHMIN']
         fhmax = config['FHMAX']
         fhout = config['FHOUT']