Bug 30398: Reindent invoices template

Bug 30398: Reindent invoices template

This patch updates the invoices template so that the indentation is
consistent.

To test, apply the patch and go to Acquisitions.

- Locate a vendor which has multiple invoices associated with it.
- View the vendor details, and click the "Invoices" link in the sidebar.
- The display of invoices should look correct. The DataTable should work
  correctly.
- Test the search filters in the sidebar to confirm that they work too.

Signed-off-by: Séverine Queune <severine.queune@bulac.fr>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>