Etsy UI not updating last modified timestamp on listing when return policy is changed through the bulk editor modal

[diegodleon]

This can be a big problem for integrations on Jan 31st, my guess is most depend on the last modified timestamp to pick which listings they import back into their apps.

Repro steps:

1. Go to Etsy UI
2. On the manage listings page, click on the small checkbox on the left down corner of a listing.
3. Click on editing options -> Exchange and return policies -> Apply a policy
4. After successful update, check the listing with the Etsy API. The last_modified_timestamp field DOES NOT change if you only edit the return policy.
5. Editing through other means such as single edit, or PATCH API DOES modify the last_modified_timestamp.