[FIX] website(_slides): delete autoplay of all iframes in the iframefallback

Delete the autoplay for all iframes in the iframefallback.
The autoplay was causing issue where the sound of the previous video
was played on the background. Now we delete the autoplay for all iframe
directly.
This happened in media_iframe_video, youtube player and vimeo videos.
We can do this for all iframe source url directly as it impacts other
modules like website_slides or website_event_track_live.

task-3012952

closes odoo/odoo#112868

Signed-off-by: Warnon Aurélien (awa) <awa@odoo.com>