play: wavesurfer audio player won't load

[Trek Hopton]

A recent change to the wavesurfer.js package that we use for our audio playback has cause it to not load correctly on our play page. For now, let’s just use the version we have been using for a while (fix it to 6.6.3), and we can look at upgrading if we need in the future.

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[Trek Hopton]

Resolved in PR #243