Loose external reference to cdn.dashjs.org

[fseydel]

The mediaelemnt and player in wp-includes/js/mediaelement/mediaelement-and-player.min.js contains an external link to ​https://cdn.dashjs.org/latest/dash.all.min.js

This introduces an external reference that's actually not needed, the file dash.all.min.js should be included locally.

I know, it's a very minor issue, but it got reported by a government issued pentest and should be easy to fix.

[Presskopp]

related #56320