Remove Balsamiq File Preview

What does this MR do and why?

The Balsamiq File Preview is not utilized a lot. In fact it has been broken since over a year on gitlab.com and on self managed instances #285525 (closed). The Balsamiq preview itself doesn't have a lot of value as it just renders the preview of the first Balsamiq page and not all the pages. We have received no user complaints whatsoever, meaning that likely noone relied on this feature.

This MR removes the previewer, as it is also riddled with tech debt, for example shipping a asm.js compiled version of sql.js

Changelog: removed

Closes #300869 (closed)

Closes #324334 (closed)

Closes #285525 (closed)

Screenshots or screen recordings

If the feature were working	Currently in Omnibus / gitlab.com	After the removal

How to set up and validate locally

N/A

MR acceptance checklist

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