[web] Display videos correctly in Multimedia component

Summary:
Context: https://linear.app/comm/issue/ENG-1512/render-video-messages-inline-on-web

Basically display media with <video> tag instead of <img> tag if mediaType === "video". Also remove any onClick functionality since we don't have any sort of full-screen video playback experience on web.

Test Plan:
Here's how it looks in Safari:

Here's how it looks in Chrome:

Made sure that images continue to look as expected.

Reviewers: tomek, ginsu, rohan, ashoat

Reviewed By: ashoat

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D5759