[yourporn] Fix video_url (closes #21645)

[v-delta]

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Closes #21645

[dstftw]

Does not work:

> py -2.7 .\youtube_dl\__main__.py https://yourporn.sexy/post/57ffcb2e1179b.html -F
[YourPorn] 57ffcb2e1179b: Downloading webpage
ERROR: Unable to extract data info; please report this issue on https://yt-dl.org/bug . Make sure you are using the latest version; see  https://yt-dl.org/update  on how to update. Be sure to call youtube-dl with the --verbose flag and include its complete output.