Their mobile site sometimes returns a different HTML response which the plugin can't handle. This varying response seems to be similar to the data which is covered by the plugin's logic for their main site, but I don't think it's worth handling this case and refactoring the plugin because of that. Requesting the same video ID on their main site seems to be working, so I instead removed all logic for the mobile site and made the plugin translate mobile input URLs to URLs for their main site.

I however don't know if this solution works reliably, not just for the input URL of #6443. So @leomani51214, since I'm not familar with okru, please go ahead and test the changes of this PR and see if any other live streams are not working because of these changes. Thank you.

$ ./script/test-plugin-urls.py okru -r ID 9544902123178
:: https://m.ok.ru/video/9544902123178
::  240p, 360p, 480p, 720p, 1080p, worst, best
:: https://mobile.ok.ru/video/9544902123178
::  240p, 360p, 480p, 720p, 1080p, worst, best
:: https://ok.ru/live/9544902123178
::  240p, 360p, 480p, 720p, 1080p, worst, best
:: https://ok.ru/video/9544902123178
::  240p, 360p, 480p, 720p, 1080p, worst, best
:: https://ok.ru/videoembed/9544902123178
::  240p, 360p, 480p, 720p, 1080p, worst, best
:: https://www.ok.ru/video/9544902123178
::  240p, 360p, 480p, 720p, 1080p, worst, best