Bug 35402: (follow-up) Remove form from returns.tt

Bug 35402: (follow-up) Remove form from returns.tt

If you have AllowReturnToBranch enabled and you check in an item which
is disallowed by the preference (returned at the wrong branch, for
instance) You get a "Cannot check in" modal.

Previously clicking the "OK" button in this form triggered JS which is
supposed to submit a form. However, all the button needs to do is
dismiss the modal. The form and the "approve" class on the button are
removed by this patch.

NOTE: This patch contains indentation changes.

To test, apply the patch and set the AllowReturnToBranch system
preference to "only at the library that the item is from."

- Locate an item belonging to another library and check it out to a
  patron.
- Check in the item.
- You should see a modal confirmation, "Cannot check in".
- Clicking the "OK" button should dismiss the modal window without
  triggering a reload of the page.

Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>