Video & Audio keep playing even after you scroll it off the screen

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Describe the bug

In Nos when you play audio or video it keeps playing even after you scroll on

To Reproduce

Steps to reproduce the behavior:

1. Go to your home feed and find a video file
2. Tap unmute
3. Tap play
4. Scroll down where the video is off the screen
5. Keep hearing the audio / video playing

Expected behavior

Video and Audio should stop playing after the media has scrolled off the screen