Use context in once in dropdown-widget.js

Problem/Motivation

In dropdown-widget.js, the makeDropdown function calls once() without passing the context.

$(once('facets-dropdown-transform', '.js-facets-dropdown-links')).each(function () {

This can cause problems in environments with BigPipe/Ajax. I'm dealing with an intermittent bug on a site now, where sometimes selecting a new option automatically triggers, sometimes it doesn't. I haven't been able to pin down exactly how this is caused, but I suspect it's related to this code not using context with once.

To fix, add context in the once call:

$(once('facets-dropdown-transform', '.js-facets-dropdown-links', context)).each(function () {

I'm not 100% certain this will address what I'm seeing, but it seems like a probably culprit. I'm not certain how much using context here is a "best practice"