custom profile fields: Remove unnecessary JSON parsing step.

Apparently, our custom profile fields feature was parsing the "user
list" field type in multiple places, and ignoring the results in one
of them.  That code had been causing some confusion; the correct
solution is to just delete it, since the template rendering process
ignores that value for this field type.

static/js/settings_account.js

@@ -96,9 +96,6 @@ exports.append_custom_profile_fields = function (element_id, user_id) {
         } else if (field_type === field_types.URL.id) {
             type = "url";
         } else if (is_user_field) {
-            if (value) {
-                value = JSON.parse(value);
-            }
             type = "user";
         } else {
             blueslip.error("Undefined field type.");