R1:5e1d94f33651

Remove nonfunctional AJAX embed behavior for Slowvote

Summary:
See <https://hackerone.com/reports/434116>. Slowvote has a piece of Javascript that attempts to let you vote on `{V123}` polls inline.

It does not work: nothing ever triggers it (nothing renders a control with a `slowvote-option` sigil).

At least for now, just remove it. It has a completely separate pathway in the controller and both pathways are buggy, so this makes fixing them easier.

Test Plan: Voted in plurality and approval polls via…