Upgrade MediaElement to 2.15.1.

Merges [29733] to the 4.0 branch.

Changes from 2.15.0:
https://github.com/johndyer/mediaelement/compare/2.15.0...2.15.1

Continues to revert upstream commit b7f82b4 to restore the status quo for Chromium support.

props wonderboymusic.
fixes #29620.

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