Vid 2099 - removing sloth from media gallery flow

We've had a number of problems with both sloth itself and with third party (UGC) js not playing nice with sloth. We've decided to removed this type of lazy loading from our flow since we're already doing a form of lazy loading with galleries by loading them with JS. 

Covers:
- https://wikia-inc.atlassian.net/browse/VID-2099
- https://wikia-inc.atlassian.net/browse/VID-2105
- https://wikia-inc.atlassian.net/browse/VID-2084