Fix the OSTree preconditions macro not populating reponame and branch

Address a regression introduced in commit 6b2fd91e "Turn the OSTree
preconditions into a list" where the iteration on the preconditions list
was done improperly.

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>

atc_renderer/templates/macros.html

@@ -8,8 +8,8 @@
   <p><kbd>$ ssh user@$DUT_IP</kbd></p>
 {% endmacro %}
 
-{% macro ostree_preconditions(precondition) %}
-{% for reponame, branch in precondition %}
+{% macro ostree_preconditions(preconditions) %}
+{% for precondition in preconditions %}
   <li class="mb-sm-2">From a PC, download and unpack the test data tarball from the gitlab test repository:</li>
   <p><kbd>$ wget https://gitlab.apertis.org/tests/{{ precondition.reponame }}/-/archive/{{ precondition.branch }}/{{ precondition.reponame }}.tar.gz</kbd></p>
   <p><kbd>$ tar -xvf {{ precondition.reponame }}.tar.gz</kbd></p>