[BUG] win_task.py delete_after=False throws Invalid value for "delete_after"

[amalaguti]

Description
Windows Minion trying to use win_task.py module to edit a Task Scheduler task, changing delete_after to False, throws
"Invalid value for "delete_after""

Setup
Windows Minion 3004.2

Steps to Reproduce the behavior
Create a Task in Task Scheduler with a trigger and setting delete_after=Immediately (or XX days), under Settings > "If the task is not scheduled to run again, delete it after:"

>salt-call --local task.edit_task "Task Name" location="\Salt" delete_after=False
local:
    Invalid value for "delete_after"

Expected behavior
The setting should be cleared

Screenshots
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Versions Report

salt --versions-report

(Provided by running salt --versions-report. Please also mention any differences in master/minion versions.)

PASTE HERE

Additional context
Add any other context about the problem here.

Possible fix:
Around these lines I did a quick fix
https://github.com/saltstack/salt/blob/master/salt/modules/win_task.py#L1128-L1137

if delete_after is not None:
      # TODO: Check triggers for end_boundary
    if delete_after is False:
        task_definition.Settings.DeleteExpiredTaskAfter = ""
    # Added else 
    else:
        if delete_after in duration:
            task_definition.Settings.DeleteExpiredTaskAfter = _lookup_first(duration, delete_after)
        else:
            return 'Invalid value for "delete_after"'