Bug 37728: (follow-up) Tell the test that opac-illrequests.tt has an op

Bug 37728: (follow-up) Tell the test that opac-illrequests.tt has an op

xt/find-missing-op-in-forms.t wants to see name="op" value="cud-..." in any
form with method="post", but opac-illrequests.tt inserts its op input by
passing around whole and unpack and repacking whole.keys which includes
the op. We just need to tell the test that it really exists.

At first, I thought of this approach as a joke, faking out the test, but
when I tried to be more responsible and put a whole <input type="hidden" etc.
in the comment, I realized that would be more likely to confuse someone
who thought that was uncommented and that they were making real changes than
it would be to future-proof against changes in the test's approach.

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Pedro Amorim <pedro.amorim@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>