[stable-only] Remove unnecessary periodic CI jobs

Since this branch is in Unmaintained phase we don't need the listed
periodic-weekly jobs to run. They can be run on-demand if needed, but
let's spare some CI resource by removing them here.

Note that periodic-stable-jobs template is also unnecessary, because
the template only runs jobs against stable branches.

Change-Id: Iabe1a62681e9d274a8ef5200eca4ca23b6dd138b

.zuul.yaml

@@ -634,7 +634,6 @@
       - openstack-cover-jobs
       - openstack-python3-zed-jobs
       - openstack-python3-zed-jobs-arm64
-      - periodic-stable-jobs
       - publish-openstack-docs-pti
       - release-notes-jobs-python3
     check:
@@ -726,12 +725,6 @@
             irrelevant-files: *nova-base-irrelevant-files
         - openstacksdk-functional-devstack:
             irrelevant-files: *nova-base-irrelevant-files
-    periodic-weekly:
-      jobs:
-        # Runs emulation feature functionality test less frequently due
-        # to being the initial release and experimental in nature.
-        - nova-emulation
-        - tempest-centos9-stream-fips
     experimental:
       jobs:
         - ironic-tempest-bfv: