StoryVideo has no video_url field and thus causes KeyError when parsing

[fireattack]

Describe the bug
As mentioned in #1238, the StoryVideo returned by single post API doesn't behave like GraphStoryVideo returned by Stories timeline either. It has no self._node['video_url'] or self._node['video_resources']. So you can only get the video from self._iphone_struct['video_versions'].

Previously you can still parse it successfully if you logged in and does not disable iPhone API, because it can still pull the videos from the iPhone API. However, after changing the line at

instaloader/instaloader/structures.py

Line 380 in f09bd51

version_urls = [self._field('video_url')]

it will errors out due to such key does not exist.

To Reproduce
Steps to reproduce the behavior:

1. find any story video and copy the URL as url

import instaloader
url = "{put URL here}"
username = '{your username}'
if m := re.search(r'https://www.instagram.com/stories/[^/]+?/(\d+?)/', .url):
    shortcode = instaloader.Post.mediaid_to_shortcode(int(m[1])) 
else:
    raise Exception(f'Cannot parse URL {url}!')
L = instaloader.Instaloader()
L.load_session_from_file(username)
post = instaloader.Post.from_shortcode(L.context, shortcode)
L.download_post(post, target='')