Bug 32291: (bug 16735 follow-up) Remove ref to library category in branches.tt

Bug 32291: (bug 16735 follow-up) Remove ref to library category in branches.tt

On bug 16735 we rewrite the library groups system. Those references in
branches.tt were part of the previous code, and they can be removed.

Test plan:
Confirm the above and that those code errors are never sent to the
template.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>