Valera/fix show captions false bug

<b>Problem</b>
When a video is set to show captions = false, in chrome, the video is large, but the captions cover 33% of the video frame.

<b>Jira issue</b>
https://edx-wiki.atlassian.net/browse/BLD-467

<b>Reviewers</b>
- @polesye