Bug 37074: Comment approval and un-approval should be CSRF-protected

Bug 37074: Comment approval and un-approval should be CSRF-protected

This patch converts the "Approve" and "Unapprove" controls in the staff
client's comment moderation page so that the operations are POST instead
of GET.

To test, apply the patch and restart services.

- If necessary, enable OPACComments and submit a few comments on a few
  titles in the OPAC
- Go to Tools -> Comments
- Test the process of approving, unapproving, and deleting comments

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>