[unmaintained-only] Periodic jobs will be weekly only

As agreed in the Neutron CI meeting, the unmaintained branches periodic
jobs will be weekly only [1].

[1]https://meetings.opendev.org/meetings/neutron_ci/2024/neutron_ci.2024-09-23-14.01.log.html#l-97

Change-Id: I5309067eb8e592076c270265c5bf8020fdc7377b
Signed-off-by: Yatin Karel <ykarel@redhat.com>

zuul.d/job-templates.yaml

@@ -43,7 +43,7 @@
         - openstack-tox-py311: # from openstack-python3-jobs template
             timeout: 3600
             irrelevant-files:  *irrelevant-files
-    periodic:
+    periodic-weekly:
       jobs:
         - openstack-tox-py39:  # from openstack-python3-jobs template
             timeout: 3600
@@ -72,7 +72,7 @@
 
 - project-template:
     name: neutron-periodic-jobs
-    periodic:
+    periodic-weekly:
       jobs: &neutron-periodic-jobs
         - neutron-functional
         - neutron-functional-with-uwsgi-fips