Fix up video on drupal-7.0 landing page

The video on https://www.drupal.org/drupal-7.0 fails to load because it is trying to use http instead of https. The multilingual captions we are using don't seem to have a usable https embed code. We'll have to switch to just the video in the meantime.

Then we should re-upload the video to the Association's YouTube account, because that's where all the DrupalCon and other videos are. It looks like YouTube supports multilingual captions without an extra wrapper. The more-simple embed will be nicer. The existing video's captions can be exported at http://www.amara.org/en/videos/NOfZXGeyeP1G/en/9977/ (if that URL breaks, the Vimeo URL to put in is http://vimeo.com/18352872).