Replace Bleach (which is deprecated) with NH3

[arthanson]

Proposed Changes

bleach is deprecated (see: mozilla/bleach#698)
https://github.com/messense/nh3 is a nice replacement

Justification

Bleach is deprecated, pre notice: "Bleach sits on top of--and heavily relies on--html5lib which is no longer in active development. It is increasingly difficult to maintain Bleach in that context and I think it's nuts to build a security library on top of a library that's not in active development. "

[github-actions]

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