Bug 30609: Reindent serial claims template

Bug 30609: Reindent serial claims template

This patch updates the serial claims template so that the indentation
is consistent. Tabs are replaced with spaces.

To test you must have at least one subscription with late issues.

- Apply the patch and go to Serials -> Claims and select the vendor
  responsible for your late issue.
- On the "Missing issues" page, confirm that everything looks correct.
- All functionality should be the same: Filters, table sorting, CSV
  export, and claim notification.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>