Bring the list of `upload_filetypes` for multisite into modernity based on .com upgrades and supported extensions for audio and video.

Fixes #24434.

Built from https://develop.svn.wordpress.org/trunk@28832


git-svn-id: http://core.svn.wordpress.org/trunk@28636 1a063a9b-81f0-0310-95a4-ce76da25c4cd