Revert "list_render: Clean up initialization."

I pushed this risk commit to the end of
a PR that had a bunch of harmless prep
commits at the front, and I didn't make
it clear enough that the last commit (this
one) hadn't been tested thoroughly.

For the list_render widget, we can simplify
the intialization pretty easily (avoid
extra sorts, for example), but the cache aspects
are still tricky on subsequent calls.

static/js/stream_edit.js

@@ -217,7 +217,7 @@ function show_subscription_settings(sub_row) {
                 }
             },
         },
-    });
+    }).init();
 
     sub_settings.find('input[name="principal"]').typeahead({
         source: () => stream_data.potential_subscribers(sub),